J O U R N A L O F C H E M I S T R Y Materials Molecular assemblies of novel amphiphilic phthalocyanines: an investigation into the self-ordering properties of complex functional materials Ziad Ali-Adib,a Guy J. Clarkson,a Neil B. McKeown,*a† Kevin E. Treacher,a Helen F. Gleesonb and Alexander S. Stennettb aDepartment of Chemistry, University of Manchester, UK M13 9PL bDepartment of Physics and Astronomy, University of Manchester, UK M13 9PL Received 17th July 1998, Accepted 18th August 1998 The synthesis and liquid crystalline properties of unsymmetrically substituted Pcs which contain both alkyl and hydroxy terminated tetra(ethyleneoxy) side-chains are described.Despite poor Langmuir–Blodgett film forming properties, the amphiphilic Pcs are of interest as they display a variety of columnar mesophases and the ability to form self-ordered lamellar films by simple solvent casting.Lamellar order can be obtained in spin-coated films of these derivatives by annealment at a temperature at which the Pc is liquid crystalline. These self-ordering spincoated films are an alternative to the laborious Langmuir–Blodgett technique for the fabrication of highly ordered and uniform films of functional molecular materials.In order to exploit the electronic or optical properties of between their liquid crystalline behaviour and the formation of ordered films. The liquid crystalline properties of the trityl- functional compounds it is necessary to understand, predict and control the structure of their condensed states. Since their protected precursors are also described.discovery seventy years ago, phthalocyanines (Pcs) have become one of the most studied of all organic functional materials. In addition to their use as blue and green colorants, Experimental Pcs are of increasing interest for applications in non-linear Liquid crystal characterisation optics, xerography, molecular electronics, photodynamic cancer therapy, solar energy conversion, catalysis and as the DiVerential scanning calorimetry measurements were made on active component of gas sensors.1 Much is now known about a Seiko DSC 220C machine and calibrated using an indium the structures of the various crystalline polymorphs of Pc and standard.Optical microscopy observations were made on a its metal ion containing derivatives.1a However, in order to Nikon Optiphot-2 microscope with a Mettler FP80 HT Hot optimise their potential utility in electronic and optoelectronic Stage.Photographs of the optical textures [Fig. 1(a)–(e)] were devices, it is necessary to fabricate Pcs as thin films in which taken using the same arrangement equipped with a Nikon the nano-scale architecture and ordering can be reproducibly FX-35 W camera.Low resolution X-ray diVraction (XRD) controlled. Vacuum sublimation1a,2 or the spin-coating of Pc from powder samples was recorded using Cu-Ka radiation particles dispersed in a soluble polymer matrix1a,3 remain the (l=1.54 A° ) from a Philips PW1130/00 generator with a nickel most important techniques for the fabrication of films derived filter.The samples were contained in glass capillaries from these insoluble compounds. However, research into the (Hilgenberg 0.01 mm thick glass, 1.0 mm outside diameter Xsynthesis of substituted Pcs has provided materials which are ray capillaries) and placed in the beam in an aluminium soluble and therefore suitable for film fabrication by the heating block. The temperature was regulated by a Control Langmuir–Blodgett (LB) technique1a,4 or by the spin-coating Techniques Process Instruments 453 Plus Thermal Controller. of pure material.1a,5 In addition, suitable substitution of the The diVracted X-rays were detected with a flat-plate photo- Pc macrocycle by flexible side-chains, either alkyl or oligo(ethy- graphic camera using Agfa-Gevaert Osray M3 X-ray film.The leneoxy), gives materials which self-order to form columnar system was calibrated using sodium chloride.High resolution mesophases.1,6 The external control over molecular orientation XRD analysis was carried out using the synchrotron radiation aVorded by liquid crystallinity may enable the fabrication of source (SRS) at Daresbury (Station 8.2, l=1.54 A° ) using monodomainal, ordered solid films.previously described methods for data collection and manipu- This paper describes the synthesis and self-ordering lation.8 The X-ray camera at the SRS was calibrated with properties of unsymmetrically substituted Pcs which contain collagen and both small and wide angle scattering data were both alkyl (hexadecyl ) and hydroxy terminated tetra(ethy- collected. The high X-ray flux available at the SRS allowed leneoxy) side-chains.These Pcs were originally designed as XRD patterns to be obtained rapidly, typically in just a few amphiphilic materials for deposition as LB multilayer films, minutes, enabling data to be collected at diVerent temperatures and their monolayer forming properties and failed attempts without any danger of sample degradation. to prepare LB films are described.Interestingly, it was discovered that they display a variety of thermotropic columnar mesophases and the ability to form self-ordered multilayer Langmuir film characterisation ( lamellar) films by simple solvent casting.7 Therefore, it was Isotherm behaviour was measured for monolayers, spread of interest to determine whether highly-ordered spin-coated from chloroform (Aldrich, HPLC grade) solution, on pure films, of uniform thickness, could be obtained from these water at pH 5.5 with no added ions using the apparatus and materials and to re-examine in more detail the relationship procedures described previously.9 Multilayer film formation was attempted on clean glass slides appropriately treated to provide either hydrophilic or hydrophobic surfaces.†E-mail: neil.mckeown@man.ac.uk J. Mater. Chem., 1998, 8(11), 2371–2378 2371Film fabrication and characterisation H; 10.54; N, 4.88%); lmax(toluene)/nm 706, 670, 644, 606, 350; dH(500 MHz, C6D6, 60°C) -0.6 (br s, 2H), 1.01 (t, 18H), Solvent cast films and spin-coated films were prepared from 1.22–1.7 (m, 144H), 1.78 (m, 12H), 2.14 (m, 12H), 3.33 (m, the same chloroform solutions (~0.02 g ml-1).The substrates 12H), 3.42 (t, 2H), 3.68 (t, 2H), 3.72 (m, 2H), 3.76 (m, 2H), were clean silicon or glass microscope slides pre-treated with 3.81–3.86 (m, 4H), 3.97 (br t, 2H), 4.35 (br t, 2H), 7.19 (tt, hexamethyldisilazane vapour. Spin-coating was achieved, at 3H), 7.70 (dd, 6H), 7.79 (d, 1H), 9.15 (br s, 1H), 9.45–9.77 5000 rpm, using a Headway Research Inc.PM80 wafer spin (br m, 7H); m/z (FAB) 2298, 13C2C153H240N8O5 (M+H+) cleaner. Glancing angle X-ray diVraction from the films was requires 2298. recorded using Cu-Ka radiation in a Philips PW1050 X-ray The third fraction was collected and applied to a fresh silica DiVractometer using a rotating intensity detector. column (eluent: toluene, 20 °C, Rf=0.30) and recrystallised from heptane to aVord 2,3,16,17-tetrakis(hexadecyl)-16,23(24)- Pc synthesis and structural characterisation bis(14,14,14-triphenyl-1,4,7,10,13-pentaoxatetradecyl)phthalocyanine 4 as a mixture of two isomers (108 mg, 3%) (Found C, Routine 1H NMR spectra were measured at 300 MHz using 79.15; H, 9.37; N, 4.86%.C150H206N8O10 requires C, 78.97; an Inova 300 spectrometer.High resolution (500 MHz) 1H H, 9.10; N, 4.91%); lmax(toluene)/nm 706, 670, 638, 608, 380, NMR spectra were recorded using a Varian Unity 500 spec- 292; dH (500 MHz, C6D6, 60°C) -1.10 (br s, 2H), 1.00 (br trometer. UV–Visible spectra were recorded on a Shimadzu t, 12H), 1.3–1.89 (br m, 104H), 2.10–2.25 (br m, 8H), UV-260 spectrophotometer using cells of pathlength 10 mm. 3.20–3.43 (br m, 8H), 3.44 (m, 4H), 3.69 (m, 4H), 3.73 (m, IR spectra were recorded on an ATI Mattson Genesis Series 4H), 3.77 (m, 4H), 3.82–3.85 (m, 8H), 4.04 (br s, 4H), 4.38 FTIR (KBr/Germanium beam splitter). Elemental analyses (br s, 4H), 7.19 (tt, 6H), 7.70 (dd, 12H), 7.83 (br s, 2H), were obtained using a Carlo Erba Instruments CHNS-O EA 8.95–9.45 (br m, 8H); m/z (FAB) 2282, 13C2C148H206N8O10 108 Elemental Analyser.Routine low resolution chemical (M++H+) requires 2281. ionisation (CI) and electron ionisation (EI ) were obtained The fourth fraction was collected and applied to a fresh using a Fisons Instruments Trio 2000. Fast atom bombardment silica column (eluent: toluene, 20 °C, Rf=0.2) and recrystal- (FAB) spectra were recorded on a Kratos Concept speclised from heptane to aVord 2,3,9,10-tetrakis(hexadecyl)- trometer.All solvents were dried and purified as described in 16(17),23(24)-bis(14,14,14-triphenyl-1,4,7,10,13-pentaoxatetra- Perrin and Armarego.10 Silica gel (60 Merck 9385) was used decyl)phthalocyanine 5 as a mixture of three isomers (268 mg, in the separation and purification of compounds by column 7.0%). (Found C, 79.06; H, 9.12; N, 4.80%.C150H206N8O10 chromatography. All Pcs were heated at 120–150 °C under requires C, 78.97; H, 9.10; N 4.80%); lmax(CH2Cl2)/nm 706, vacuum for 18 h as the final step of purification. 670, 638, 608, 380, 344, 292; dH(500 MHz, C6D6, 60°C)-1.10 4-(14,14,14-Triphenyl-1,4,7,10,13- (2H, br s), 1.00 (t, 12H), 1.34–1.89 (br m, 104H), 2.10–2.25 pentaoxatetradecyl)phthalonitrile 1 (br m, 8H), 3.26–3.40 (br m, 8H), 3.44 (m, 4H), 3.69 (m, 4H), 3.73 (m, 4H), 3.77 (m, 4H), 3.82–3.85 (m, 8H), 3.95–4.06 To a solution of 4-nitrophthalonitrile (1.4 g, 8.0 mmol, (br m, 4H), 4.34–4.50 (br m, 4H), 7.18 (tt, 6H), 7.70 (dd, Aldrich) and tetraethylene glycol monotrityl ether11 (3.4 g, 12H), 7.76 (br s, 2H), 8.95–9.65 (br m, 8H); m/z (FAB) 2283, 8.0 mmol) in anhydrous DMF (30 ml ) was added anhydrous 13C2C148H206N8O10 (M++H+) requires 2281.potassium carbonate (2 g, 14.5 mmol) and the mixture stirred The fifth fraction was collected and applied to a fresh silica under nitrogen for 6 days at 50 °C. Water was added (100 ml ) column (eluent: toluene–THF, 2051, 20 °C, Rf=0.2) and and the mixture extracted with Et2O (3×60 ml ), washed with recrystallised from heptane to aVord 2,3-bis(hexadecyl)- water (2×50 ml ) and dried over anhydrous magnesium sulf- 9(10),16(17),23(24)-tris(14,14,14-triphenyl-1,4,7,10,13-pentaate. The solvent was removed and the product recrystallised oxatetradecyl)phthalocyanine 6 as a mixture of four isomers from hexane–toluene (251) to give 1 as colourless plates (2.1 g, (298 mg, 8%).(Found C, 76.44; H, 7.38; N, 4.86%. 47%), mp 92–94 °C; n (KBr)/cm-1 2230 (CON) (Found C, C145H172N8O15 requires C, 76.82; H, 7.65; N, 4.94%); 74.55; H, 6.41; N, 5.02%. C35H34N2O5 requires C, 74.71; H, lmax(toluene)/nm 707, 671, 638, 610, 380, 344; dH(500 MHz, 6.09; N, 4.98%); dH(200 MHz, CDCl3) 3.21 (t, 2H), 3.64–3.70 C6D6, 60°C) -1.45 (br s, 2H), 1.00 (t, 6H), 1.34–1.89 (br (m, 10H), 3.84 (t, 2H), 4.04 (t, 2H), 7.05 (dd, 1H), 7.10 (d, m, 52H), 2.15–2.23 (br m, 4H), 3.22–3.40 (br m, 4H), 3.44 1H), 7.19 (t, 3H), 7.26 (t, 6H), 7.45 (d, 6H), 7.57 (d, 1H); (m, 6H), 3.68 (m, 6H), 3.74 (m, 6H), 3.77 (m, 6H), 3.82–3.85 m/z (CI) 580 (M++NH4+). (m, 12H), 3.90–4.08 (br m, 6H), 4.34–4.50 (br m, 6H), 7.18 (tt, 9H), 7.70 (dd, 18H), 7.76 (br m, 3H), 8.95–9.65 (br m, Phthalocyanines 2–7 8H); m/z (FAB) 2269, 13C2C143H172N8O15 (M++H+) requires 2267.To a rapidly stirred mixture of compound 1 (2.0 g, 3.55 mmol) and 4,5-bis(hexadecyl )phthalonitrile6c (1.9 g, 3.39 mmol) in The sixth fraction was collected and applied to a fresh silica column (eluent: toluene–THF, 1051, 20 °C, Rf=0.2) and refluxing pentanol (10 ml ), under a nitrogen atmosphere, was added excess lithium metal (0.2 g). Heating and stirring were recrystallised from heptane to aVord 2,9(10),16(17), 23(24)- tetrakis ( 14,14,14-triphenyl-1,4,7,10,13-pentaoxatetradecyl)- continued for 6 h.On cooling, water (30 ml ) was added and the reaction mixture heated to ensure complete removal of phthalocyanine 7 as a mixture of four isomers (105 mg, 3%) (Found C, 74.33; H, 6.12; N, 5.01%.C140H138N8O20 requires lithium ions from the central cavity of the Pcs. Evaporation of the water, under reduced pressure, left a green product C, 74.65; H, 6.18; N, 4.97%); lmax(toluene)/nm 704, 668, 646, 608, 384, 344; dH(500 MHz, C6D6, 60°C) -2.5 (br s, 2H), mixture. The resultant solid was dissolved in toluene and passed through a silica column, at 50 °C, using an eluent 3.45 (m, 8H), 3.70 (m, 8H), 3.76 (m, 8H), 3.81 (m, 8H), 3.89 (m, 16H), 4.00–4.15 (8H, br m), 4.32–4.51 (br m, 8H), 7.20 composed of an increasing amount of THF relative to toluene.The first fraction (85 mg, 2%) (Rf=0.9, 50 °C, toluene) (tt, 12H), 7.71 (dd, 24H), 7.76 (br m, 4H), 8.82–9.51 (m, 8H); m/z (FAB) 2254, 13CC138H138N8 O20 (M++H+) proved to be identical to a previously prepared sample of 2,3,9,10,16,17,23,24-octakis(hexadecyl)phthalocyanine 2.1g requires 2254.The second fraction was collected and applied to a fresh silica column (eluent: toluene–heptane, 151, 50 °C, Rf=0.5) 2,3,9,10,16,17-Hexakis(hexadecyl )-23-(12-hydroxy-1,4,7,10- and recrystallised from heptane to aVord 2,3,9,10,16,17-hexakis- tetraoxadodecyl)phthalocyanine 8 (hexadecyl)-23-(14,14,14-triphenyl-1,4,7,10,13-pentaoxatetradecyl) phthalocyanine 3 as a blue solid (316 mg, 8%).(Found A solution of compound 3 (200 mg, 95 mmol), THF (30 ml ) and hydrochloric acid (1 ml, 10 mol l-1) was heated at reflux C, 81.30; H, 10.70; N, 4.89%. C155H240N8O5 requires C, 81.10; 2372 J. Mater. Chem., 1998, 8(11), 2371–2378for 1 h. On cooling, the solvent was removed under reduced Results and discussion pressure and the resulting solid redissolved and eluted through Pc synthesis a silica column (eluent5toluene–THF). Recrystallisation from heptane gave 8 as a blue solid (160 mg, 82%) (Found C, 79.81; Pcs 2–12 are prepared by the route shown in Scheme 1.An H, 10.82; N, 5.40%. C136H226N8O5 requires C, 79.94; H; 10.66; aromatic nucleophilic substitution reaction6f,12 between tetra- N, 5.49%); llmax(toluene)/nm 706, 670, 644, 606, 350; ethylene glycol monotrityl ether and commercially available dH(500 MHz, C6D6, 60°C) -0.8 (br s, 2H), 1.00 (t, 18H), 4-nitrophthalonitrile provides the important precursor 1.22–1.7 (m, 144H), 1.78 (m, 12H), 2.14 (m, 12H), 3.33 (m, 4-(14,14,14-triphenyl-1,4,7,10,13-pentaoxatetradecyl )phthalo- 12H), 3.51 (t, 2H), 3.61 (t, 2H), 3.66 (m, 2H), 3.73 (m, 2H), nitrile 1.The mixed cyclotetramerisation of 4,5-bis- 3.82 (m, 2H), 3.98 (br t, 4H), 4.40 (br t, 2H), 7.82 (d, 1H), (hexadecyl )phthalonitrile and 1 gives a complex product 9.08 (br s, 1H), 9.45–9.77 (br m, 7H), signal of hydroxy mixture from which Pcs 2–7 are readily separated by simple proton hidden by alkyl resonances.column chromatography.6g The trityl protecting groups are removed from 2–7 under acid catalysed hydrolytic conditions 2,3,16,17-Tetrakis(hexadecyl )-9,23-(12-hydroxy-1,4,7,10- to give the amphiphilic Pcs 8–12, respectively. The structure tetraoxadodecyl)phthalocyanine 9 and purities of Pcs 2–12 were confirmed by fast atom bombardment mass spectrometry (FABMS), high resolution 1H NMR Pc 9 was prepared from 4 by a similar procedure to that for (500 MHz) and UV–VIS absorption spectroscopy, elemental 8 and recrystallised from toluene (39 mg, 62%) (Found C, analysis and HPLC (purity >99%).NMR analysis is consist- 74.58; H, 9.71; N,6.42%. C112H178N8O10 requires C, 74.87; H, ent with Pcs 4 and 9 being composed of a statistical mixture 9.99; N, 6.24%); lmax(toluene)/nm 708, 672, 642, 610, 384, of two inseparable regioisomers and Pcs 5 and 10 being 344; dH(500 MHz, C6D6, 60°C) -1.8 (br s, 2H), 1.00 (t, composed of three inseparable regioisomers.The separation 12H), 1.30–1.89 (br m, 104H), 2.10–2.25 (br m, 8H), of opposite (4 and 9) and adjacent (5 and 10) isomers contain- 3.10–3.43 (br m, 8H), 3.50 (m, 4H), 3.67 (m, 4H), 3.71 (m, ing both oligo(ethyleneoxy) and alkyl side chains has been 4H), 3.78 (m, 4H), 3.82–3.86 (m, 8H), 4.06 (br s, 4H), 4.45 demonstrated previously.6g Pc 8 is insuYciently soluble in cold (br s, 4H), 7.85 (br s, 2H), 8.85–9.45 (br m, 8H), signal of solvents to allow investigations into the fabrication of LB and hydroxy proton hidden by alkyl resonances; m/z (FAB) 1796, spin-coated films derived from this compound. 13C2C110H178N8O10 (M++H+) requires 1797. Mesophase properties 2,3,9,10-Tetrakis(hexadecyl )-16,23-bis(12-hydroxy-1,4,7,10- tetraoxadodecyl)phthalocyanine 10 All of the Pcs 2–12 display at least one thermotropic mesophase. The transition temperatures and enthalpies, as measured Pc 10 was prepared from 5 by a similar procedure to that for by diVerential scanning calorimeter (DSC), are given in 8 and recrystallised from toluene (94 mg, 80%) (Found C, Table 1.Polarising optical microscopy of these materials gave 74.59; H, 9.69; N, 6.04%. C112H178N8O10 requires C, 74.87; in total four distinct optical textures, only one of which is H, 9.99; N 6.24%); lmax (CH2Cl2)/nm 706, 670, 638, 608, 384, easily assigned as that of a columnar hexagonal mesophase 344, 292; dH(500 MHz, C6D6, 60°C) -1.40 (2H, br s), 1.00 [Qh;13 Fig. 1(a) and 2(a)]. Low resolution powder X-ray (t, 12H), 1.34–1.89 (br m, 104H), 2.10–2.30 (br m, 8H), diVraction (XRD) studies of each Pc were carried out, however 3.26–3.40 (br m, 8H), 3.55 (m, 4H), 3.65 (m, 4H), 3.69 (m, these failed to give adequate information for structural eluci- 4H), 3.77 (m, 8H), 3.85 (m, 4H), 3.86 (br m, 4H), 4.00–4.50 dation of the other mesophases.Therefore, high resolution (br m, 4H), 7.60–7.75 (br s, 2H), 8.75–9.65 (br m, 8H), measurements were made using a synchrotron X-ray source signal of hydroxy proton hidden by alkyl resonances; m/z for Pcs 2 and 8–11. These results and the low resolution data (FAB) 1797, 13C2C110H178N8O10 (M++H+) requires 1797. for Pcs 3–7 and 12 are collected in Table 2.High resolution XRD measurements confirm that the 2,3-Bis(hexadecyl )-9,16,23-tris(12-hydroxy-1,4,7,10- symmetrical Pc 2 has two distinct mesophases. Previously tetraoxadodecyl)phthalocyanine 11 there was some doubt as to whether the lower temperature Pc 11 was prepared from 6 by a similar procedure to that for mesophase of 2 was simply a textural variation of Qh,6g in 8 and recrystallised from toluene (79 mg, 68%) (Found C, analogy with behaviour displayed by 1,4,8,11,15,18,22,25- 68.64; H, 8.34; N, 7.14%.C88H130N8O15 requires C, 68.63; H, octaalkyl-Pcs.15 However, the two distinct small angle diVrac- 8.51; N, 7.28%); lmax(toluene)/nm 706, 670, 638, 608, 384, tion rings, observed by high resolution XRD, are assignable 346, 292; dH(500 MHz, C6D6, 60°C) -3.3 (br s, 2H), 1.00 to diVraction from the 200 and 110 planes of a rectangular (t, 6H), 1.34–2.3 (br m, 52H), 2.80–3.31 (br m, 4H), 3.65 lattice.These reflections would be coincident for a hexagonal (m, 6H), 3.74 (m, 6H), 3.78 (m, 6H), 3.86 (m, 6H), 3.95 (m, mesophase. The ‘striated focal conic’ optical texture [Fig. 1(b)] 12H), 3.99–4.21 (br m, 6H), 4.30–4.58 (br m, 6H), 7.46–7.82 has been associated with a columnar rectangular mesophase (br m, 3H), 8.00–9.65 (br m, 8H), signal of hydroxy with a P21/a plane group symmetry [Qr(P21/a , Fig. 2(b)].14 proton hidden by alkyl resonances; m/z (FAB) 1541, However, we did not observe a reflection from 210 for this or 13C2C86H130N8O15 (M++H+) requires 1541. the lower temperature mesophase of amphiphilic Pcs 9 which also displays the striated focal conic texture.The lack of a 2,9,16,23-Tetrakis(12-hydroxy-1,4,7-tetraoxadodecyl )- reflection from the 210 plane suggests C2/m plane group phthalocyanine 12 symmetry [Qr(C2/m), Fig. 2(c)], although it has been noted in previous studies of the Qr(P21/a) mesophase that diVraction Pc 12 was prepared from 7 by a similar procedure to that for from the 210 plane can be very weak and may not be 8 and recrystallised from THF–toluene (45 mg, 65%) (Found C, 59.53; H, 6.59; N, 8.47%.C64H82N8O20 requires C, 59.90; H, 6.44; N, 8.73%); lmax(CH2Cl2)/nm 704, 670, 646, 608, 384, 344; dH(500 MHz, d6-DMSO, 80 °C) -3.1 (br s, 2H), 3.50–3.60 (m, 8H), 3.70 (m, 8H), 3.75 (m, 8H), 3.85 (m, 8H), 3.94 (m, 8H), 4.20 (b m, 8H), 4.33 (b m, 8H), 4.66 (br m, CN CN O2N CN CN Tr(OCH2CH2)3O ii, iii 2 + 3–7 iv 8–12 i 8H,), 7.50–7.69 (b m, 4H), 8.10–8.29 (b m, 4H), 8.50–8.70 Scheme 1 Reagents and conditions: i, Tr(OCH2CH2)3OH, anhydrous (br m, 4H), signal of hydroxy proton hidden by alkyl reson- K2CO3, DMF, 50–70 °C; ii, 4,5-Bis(hexadecyl )phthalonitrile, lithium, ances; m/z (FAB) 1283, 13CC63H82N8O20 (M++H+) pentanol, 135 °C; iii, acetic acid, separation by chromatography; iv, HCl (aq), THF, reflux.requires 1284. J. Mater. Chem., 1998, 8(11), 2371–2378 2373N N N N N N N N H H R R R R R R R R N N N N N N N N H H R R R R R R N N N N N N N N H H O(CH2CH2O)3X R R R R X(OCH2CH2)3O N N N N N N N N H H O(CH2CH2O)3X R R R R O(CH2CH2O)3X N N N N N N N N H H R R X(OCH2CH2)3O O(CH2CH2O)3X N N N N N N N N H H O(CH2CH2O)3X X(OCH2CH2)3O O(CH2CH2O)3X O(CH2CH2O)3X 2 R = C16H33 3 X = -Trityl, R = C16H33 8 X = -H, R = C16H33 4 X = Trityl, R = C16H33 9 X = H, R = C16H33 5 X = Trityl, R = C16H33 10 X = H, R = C16H33 6 X = Trityl, R = C16H33 11 X = H, R = C16H33 7 X = Trityl 12 X = H O(CH2CH2O)3X O(CH2CH2O)3X discernible from the background ‘noise’.16 Therefore, we whereas 10 displays a monotropic Qh which is stable over only a few degrees.The stable higher temperature mesophase of 10 has denote this mesophase simply as Qr1. For the lower temperature mesophase of Pc 11, which displays the striated focal conic a ‘mosaic’ texture with large domain size [Fig. 1(c)]. High resolution XRD analysis allows assignment of some diVraction texture of Qr1, there is a weak diVraction assignable to the 210 plane suggesting P21/a symmetry.In addition, there is a strong peaks to a rectangular lattice but additional small angle diVractions (d-spacings=52.2 and 47.7 A° ) may be due to a bilayer diVraction (d-spacing=54.0 A° ) which appears to originate from the 100 plane of the rectangular lattice. Reflection from lamellar superstructure. This mesophase is denoted as Qr2. The lower temperature mesophase of 10 is characterised by a granular this plane is not consistent with the extinction rules17 for a rectangular lattice of P21/a or C2/m plane symmetry group texture [Fig. 1(d)] superimposed on the mosaic texture of the Qr2 mesophase on cooling.We initially described this as a bilayer and suggests additional bilayer lamellar ordering.A much weaker reflection from the 100 plane is also observed in the lamellar mesophase (QL) on the basis of low resolution XRD analysis and the pronounced lamellar self-ordering properties of Qh mesophase of 11 perhaps resulting from the asymmetry of the molecule and indicating segregation of the two types of this compound.7 However, high resolution XRD shows diVractions originating from further ordering (d-spacings=47.2 and side-chain even at high temperature.Pc 10 possesses exceptional mesophase behaviour. Most Pc 23.7 A° ) in addition to the stronger lamellar diVractions (dspacings= 57.2, 28.6 and 19.2 A° ). mesogens have a Qh mesophase over a broad temperature range 2374 J. Mater. Chem., 1998, 8(11), 2371–2378Table 1 Mesophase transition temperatures (°C) with enthalpy changes (DH/J g-1) in parentheses.K=crystal, QL=columnar lamellar mesophase, Qr1=columnar rectangular mesophase which displays striated focal conic texture [Fig. 1(b)], Qr2=columnar rectangular mesophase which displays mosaic texture [Fig. 1(c)]; Qh=columnar hexagonal mesophase. Transition temperature and enthalpies for the heating cycle. Pc Glass–Qh K–QL K–Qh K–Qr1 Qr1–Qh QL–Qr2 Qr2–I Qh–I 2 — — — 108 (96) 170a — — 196 (6) 3 — — — 86 (120) 89a — — 167 (3) 4 — — — 41 (81) 191 (1) — — 196 (3) 5 — — — 77 (88) — — — 152 (3) 6 — — — 32 (23) 76 (1) — — 177 (1) 7 30b — — — — — — 225(1) 8 — — — 81 (120) 107 (2) — — 189 (3) 9 — — — 71 (30) 109 (3) — — 234 (5) 10c — 79 (88) — — — 132 (1) 194 (4) — 11 — — — 80 (16) 252 (1) — — 273 (1) 12 — — 75(14) — — — — >320 aTransition not observed by DSC.bGlass transition temperature. cPc 10 also displays a monotropic Qh mesophase on cooling from the isotropic liquid. All of the Pc mesophases display broad wide-angle cofacial ordering of the Pc molecules within the molecular stacks. Previous studies have suggested that alkoxy substituted diVraction rings correlating to d-spacings of 4–5 A° .The mesophases of Pcs 6, 7, 11 and 12 display an additional sharp wide Pc mesogens are able to form relatively ordered columnar structures due to the smaller steric demand of the oxygen angle diVraction ring corresponding to 3.5 A° which indicates an untilted columnar structure in which there is significant linking group as compared to the methylene group of alkyl Table 2 Powder X-ray diVraction data for Pcs 2–12.Each diVraction is given in A° ngstrom units. For each mesophase the assignments are based on a rectangular lattice, but for the mesophase and solid phase assignments of Pcs 9–11 a lamellar structure is also considered. Pc Phase T / °C Observed d-spacings/A° (assignments) 2-D lattice dimensions/A° 2a Qh 30.0 17.3 15.0 4–5 b=34.6 (190) (110/200) (310/020) (400/220) a=Ó3b Qr1 31.3 28.9 18.3 16.3 4–5 a=62.6 (140) (200) (110) (310) (020) b=32.5 3b,c Qh 29.2 16.8 14.3 4–5 b=33.7 (120) (110/200) (310/020) (400/220) a=Ó3b 5b Qh 29.5 17.0 14.6 4–5 b=34.1 (120) (110/200) (310/020) (400/220) a=Ó3b 6b Qh 29.6 16.8 14.3 4–5 3.5 b=34.2 (130) (110/200) (310/020) (400/220) a=Ó3b Qr1 28.5 23.1 15.1 4–5 3.5 a=57.0 (60) (200) (110) (310) b=25.3 7b Qh 28.5 16.9 14.3 4–5 3.5 b=32.9 (120) (110/200) (310/020) (400/220) a=Ó3b glass 8.5 16.9 14.3 4–5 3.5 b=32.9 (25) (110/200) (310/020) (400/220) a=Ó3b 8b Qh 28.5 16.6 14.3 4–5 b=32.9 (150) (110/200) (310/020) (400/220) a=Ó3b Qr1 30.8 28.5 18.0 16.0 4–5 a=61.6 (100) (200) (110) (310) (020) b=32.1 9a Qh 29.7 17.1 15.1 4–5 b=34.3 (200) (110/200) (310/020) (400/220) a=Ó3b Qr1 27.9 23.1 15.0 4–5 a=55.8 (90) (200) (110) (310) b=25.4 Solid 29.8 15.1 4–5 L=29.8 (25) (n=1) (n=2) 10a Qr2 52.2 47.7 28.5 21.0 16.8 4–5 a=52.2 (180) (100, n=1) (?) (110) (210) (020) b=34.0 (L=52.2) QL 57.2 47.2 28.6 23.7 19.2 4–5 L=57.2 (120) (n=1) (?) (n=2) (?) (n=3) Solid 50.2 46.5 25.4 16.8 4–5 L=50.2 (25) (n=1) (?) (n=2) (n=3) 11a Qh 53.0 26.5 15.3 4–5 3.5 b=30.6 (265) (100, n=1) (110/200) (310/020) a=Ó3b (L=53) Qr1 54.0 27.2 25.5 19.5 17.6 3–5 a=54.0 (230) (100, n=1) (200, n=2) (110) (210) (300, n=3) b=28.8 (L=54.0) Solid 51.8 26.0 17.3 4–5 3.5 (L=51.8) (30) (n=1) (n=2) (n=3) 12b Qh 23.0 4–5 3.5 b=26.6 (200) (110/200) a=Ó3b aHigh resolution XRD using SRS.bLow resolution XRD. cLower temperature mesophase is stable over too small a range for XRD analysis on low resolution equipment.J. Mater. Chem., 1998, 8(11), 2371–2378 2375Fig. 1 The optical texture of (a) the Qh mesophase (Pc 2, 187 °C), (b) the Qr1 mesophase (Pc 2, 160 °C), (c) the Qr2 mesophase (Pc 10, 150 °C), (d) the QL mesophase (Pc 10, 120 °C) and (e) the lyotropic Nc mesophase of Pc 12 which appears between the isotropic dilute ethanolic solution and the pure material (right of micrograph).All textures observed through crossed polarisers at a magnification of ×100. substituted Pcs.16 The wide-angle XRD results of Pcs 6 and 11 Similar anisotropic glass formation has been described recently for Pcs containing large dendritic substituents.19 suggest that two alkyl substituents are insuYcient to reduce the intermolecular ordering within the columnar mesophase.Pc 12 is soluble in protic polar solvents such as ethanol. The analysis of concentrated ethanolic solutions of Pc 12 by Pc 7 forms an anisotropic glass, on cooling from the mesophase, in which the ordered structure of the Qh mesophase polarising optical microscopy shows a ‘marbled’ texture [Fig. 1(e)] which is one of the characteristic textures of the is frozen.DSC shows clearly the reversible glass transition and XRD indicates the hexagonal columnar structure of the columnar nematic lyotropic mesophase [Nc; Fig. 2(d)].1f UV–VIS analysis of dilute ethanolic solutions of Pc 12 resulting brittle solid.18 The bulky nature of the four large trityl end-groups appears responsible for this behaviour. (lmax=620 nm) indicates the presence of the columnar aggre- 2376 J.Mater. Chem., 1998, 8(11), 2371–2378area per molecule can be estimated as 93 A° from the intercolumnar distance (26.5 A° ) and the cofacial intermolecular distance (3.5 A° ) of the hexagonal mesophase of Pc 12 (Table 2). These estimated areas per molecule (Aest) are in reasonable agreement with the observed values of A0 and A30 for Pcs 10 and 11 (Table 3).The observed values of A0 and A30 for Pc 9 (Table 3) also imply a perpendicular orientation of the Pc molecules in its monolayer (estimated area=155 A° 2) rather than a parallel orientation (estimated minimum area=225 A° 2) that would allow both tetra(ethyleneoxy) side-chains to be immersed simultaneously. For Pcs 9, 10 and 11 the Langmuir isotherms are characterised by a lack of hysteresis and good monolayer stability for prolonged periods of time at a surface pressure of 30 mN m-1. Despite these encouraging monolayer properties, multilayer films of Pcs 9, 10 and 11 could not be deposited onto either hydrophilic or hydrophobic substrates. In each case, successful deposition on the up stroke was followed by the loss of the material on the down stroke.This was the case even after allowing the initially deposited monolayer to dry for over 1 h. It should be noted that conventional oligo(ethyleneoxy)-based non-ionic surfactants are also poor LB film forming materials.20 Order in solvent cast and spin-coated films The simple process of forming films cast from chloroform Fig. 2 (a) Columnar hexagonal mesophase (Qh, a=Ó3b), (b) columnar rectangular mesophase with P21/a plane group symmetry, (c) rectangu- solutions (20 mg ml-1) of Pcs 9, 10 and 11 onto clean, lar disordered with C2/m plane group symmetry and (d) columnar hydrophobic substrates gives films with a high degree of nematic mesophase (Nc).lamellar ordering—as indicated by glancing angle XRD. Films cast onto hydrophilic substrates show no evidence of a lamellar structure, suggesting that in the ordered films the non-polar gates which are a prerequisite for the formation of the Nc hexadecyl side-chains of the first monolayer are in contact mesophase.with the surface of the substrate. For the cast films of Pcs 10 and 11, the large d-spacings are consistent with a bilayer Langmuir–Blodgett film forming properties structure in which the Pc molecules are oriented perpendicular The LB technique, which involves film fabrication by the to the surface of the substrate. Pc 9 gives a cast film for which sequential deposition of a monolayer formed at an air–water the d-spacing is consistent with a monolayer structure interface, has been thoroughly investigated as a method of (Table 4).The formation of a bilayer from Pc 9 is disfavoured preparing multilayer films derived from soluble Pc deriva- by its substitution pattern which places side-chains of similar tives.1a,4 It is apparent that an amphiphilic character is highly polarity on opposite sides of the molecule. The apparent advantageous for obtaining a truly ordered multilayer film.4d–f degree of ordering within these films can be increased by Thus, the LB film forming properties of soluble amphiphilic annealing for a short time at a temperature at which the Pcs 9, 10 and 11 were studied. material is mesogenic (Fig. 3, Table 4).7 However, these sol- Table 3 summarises the important Langmuir isotherm vent cast films are of non-uniform thickness. A number of parameters of area per molecule extrapolated to a surface recent studies have indicated that spin coating is a useful pressure of 0 mN m-1 (A0), the area per molecule at a surface technique for the preparation of films of uniform thickness pressure of 30 mN m-1 (A30) and the collapse pressure (pc) derived from soluble Pcs.5 These films proved to be amorphous for the monolayer.For each Pc these figures are consistent or microcrystalline in structure. with the formation of a stable molecular monolayer at the Spin-coated films of Pcs 9–11 on hydrophobic substrates do air–water interface in which the Pc molecules are oriented not show any evidence of long-range order by glancing angle approximately perpendicular to the water surface.For Pc 10, XRD and the films appear non-birefringent by polarising assuming that both hydrophilic tetra(ethyleneoxy) chains are optical microscopy.Annealing the films for a short period of immersed in the water, the eVective area per molecule would time at a temperature at which the Pc is liquid crystalline be determined by the four hydrophobic hexadecyl chains. This value can be estimated as 155 A° 2 from the intercolumnar Table 4 Glancing angle XRD data for solvent cast and spin coated distance (35.5 A° ) and the cofacial intermolecular distance films of Pcs 9–11 after annealment in their mesophase (4.5 A° ) of the hexagonal mesophase of symmetrical Pc 2 (Table 2).Similarly for Pc 11, assuming that all three tetra- Film Lamellar Orders of Intensitya (ethyleneoxy) chains are immersed in the water, the eVective Pc fabrication d-spacing/A° diVraction (arbitrary units) 9 cast 29.5 2 838 Table 3 The monolayer (Langmuir isotherm) properties of the 9 spin coated 30.2 2 120b amphiphilic Pcs 9–11 at the air-water interface. The estimated values 10 cast 49.7 4 458 for the molecular area (Aest) are derived from the appropriate XRD 10 spin coated 48.6 3 85b data (see text). 11 cast 51.3 5 813c 11 spin coated 50.0 5 155b,c Pc A0/A° 2 A30/A° 2 Aest/A°2 pc/mN m-1 aIntensity of the first order diVraction peak.bThe spin coated films are significantly thinner than the solvent cast films, which may 9 154 140 155 43 10 143 122 155 49 account for the lower intensity of the diVraction peaks from these film. cSecond order diVraction peak is more intense by ~20%. 11 99 85 93 53 J.Mater. Chem., 1998, 8(11), 2371–2378 2377M. Hanack, Struc. Bonding, 1991, 74, 41; (d) C. Van Nostrum and R. J. M. Nolte, Chem. Commum., 1996, 2385. 2 S. Dogo, J. P. Germain, C. Maleysson and A. Pauly, Thin Solid Films, 1992, 219, 244. 3 N. Minami. K. Sasaki and K. Tsuda, J. Appl. Phys., 1983, 54, 6764. 4 (a) R. H. Tredgold, Order in Thin Organic Films, Cambridge University Press, Cambridge, 1994; (b) A.Ulman, Introduction to Ultrathin Organic Films, Academic Press, San Diego, 1991; (c) S. Baker, M. C. Petty, G. G. Roberts, M. V. Twigg, Thin Solid Films, 1983, 99, 53; (d) M. J. Cook, M. F. Daniel, K. J. Harrison, N. B. McKeown and A. J. Thompson, J. Chem. Soc., Chem. Commun., 1987, 1148; (e) J. D. Shutt, D. A. Batzel, R. V. Sudiwala, S. E. Rickert and M.E. Kenney, Langmuir, 1988, 4, 1240; ( f ) N. B. McKeown, M. J. Cook, A. J. Thomson, K. Fig. 3 Glancing angle X-ray diVractograms from the solvent cast films J. Harrison, M. F. Daniel, R. M. Richardson and S. J. Roser, Thin of Pcs (a) 9, (b) 10 and (c) 11 after heating at a temperature at which Solid Films, 1988, 159, 469; (g) P. A. Albouy, J. Phys. Chem., the Pc displays a columnar mesophase. 1994, 98, 8543; (h)M.Burghard,M. Schmelzer, S. Roth, P. Haisch and M. Hanack, Langmuir, 1994, 10, 4265. 5 S. M. Critchley, M. R. Willis, M. J. Cook, J. McMurdo and Y. Maruyama, J. Mater. Chem., 1992, 2, 157; S. M. Critchley, results in the formation of highly ordered films which possess M. R. Willis, Y. Maruyama, S. Bandow, M. J. Cook and both the lamellar structure of the solvent cast films (Table 4) J.McMurdo, Mol. Cryst. Liq. Cryst., 1993, 230, 287; M. J. Cook, and the uniform thickness of the unannealed spin-coated films. J. Mater. Chem., 1996, 6, 677. As such, these films are reminiscent of LB multilayers but are 6 (a) J. Simon and C. Piechocki, J. Am. Chem. Soc., 1982, 104, 5245; much easier to fabricate. There is reasonable agreement (b) M.J. Cook, M. F. Daniel, K. J. Harrison, N. B. McKeown and A. J. Thompson, J. Chem. Soc., Chem. Commun., 1987, 1086; between the lamellar spacings in the annealed films, solid and (c) K. Ohta, L. Jacquemin, C. Sirlin, L. Bosio and J. Simon, New lower temperature mesophases for Pcs 9–11 (Table 2 and 4). J. Chem., 1988, 12, 751; (d) J. F. Van der Pol, E. Neeleman, Clearly, the attainment of high lamellar order during J.W. Zwikker, R. J. M. Nolte, W. Drenth, J. Aerts, R. Visser and annealment is due to the self-ordering within the lower tem- S. J. Picken, Liq.Cryst., 1989, 6, 577; (e) A. N. Cammidge, perature mesophase of the Pc resulting in segregation of the M. J. Cook, K. J. Harrison and N. B. McKeown, J. Chem. Soc., non-polar hexadecyl side-chains from the polar hydroxy ter- Perkin Trans. 1, 1991, 3053; ( f ) N. B. McKeown and J. Painter, J. Mater. Chem., 1994, 4, 209; ( g) G. J. Clarkson, N. B. McKeown minated tetra(ethyleneoxy) side-chains. Similar eVects have and K. E. Treacher, J. Chem. Soc., Perkin Trans. 1, 1995, 1817; been observed in solvent cast films composed of other types (h) G. J. Clarkson, B. M. Hassan, D. R. Maloney and of amphiphilic molecules such as phospholipids.21 UV–VIS N.B. McKeown, Macromolecules, 1996, 29, 1854. spectra of the annealed films derived from Pcs 9–11 show that 7 K. E. Treacher, G. J. Clarkson, Z. Ali-Adib and N. B.McKeown, the major absorption (Q-band) is at 620 nm, shifted by exciton Chem. Commun., 1996, 73. interactions to a lower wavelength compared to the main 8 W.Bras, G. E. Derbyshire, A. J. Ryan, G. R. Mant, P. Manning, R. E. Cameron and W. Mormann, J. Phys., 1993, 3, 447; absorption band of their solution spectra (lmax=704 nm), A. S. Stennett, PhD thesis, University of Manchester (UK), 1998. indicating that the Pc molecules are in a columnar arrangement 9 F. Davies, P. Hodge, C. R. Towns and Z. Ali-Adib, within the solid lamellar structure.7 Macromolecules, 1991, 24, 5695. 10 D. D. Perrin and W. L. F. Armarego, Purification of Laboratory Chemicals, 3rd edn., Pergammon, Oxford, 1988. Conclusions 11 N. Jayasuriya, S. Bosak and S. L. Regen, J. Am. Chem. Soc., 1990, 112, 5844. The combination of spin-coating technology with meso- 12 W. O. Siegl, J. Heterocycl. Chem., 1981, 18, 1613; A. W. Snow and morphic ordering can produce highly ordered and uniform N.L. Jarvis, J. Am. Chem. Soc., 1984, 106, 4706; M. D. Pace, films of non-uniformly substituted Pcs 9–11. The antipathy W. R. Barger and A. W. Snow, Langmuir, 1989, 5, 973; of two types of side-chains which have diVerent polarity S. M. Marcuccio, P. I. Svirskaya, S. Greenberg, A. B. P. Lever induces lamellar ordering both within the columnar liquid and K.B. Tomer, Can. J. Chem., 1985, 63, 3057; C. C. LeznoV, crystal and the solid phase of these derivatives. This phenom- S. Greenberg, S. M. Marcuccio, P. C. Minor, P. Seymour and A. B. P. Lever, Inorg. Chim. Acta, 1984, 89, L35. enon can be used to form self-ordering spin-coated films which 13 The symbol Q has recently become the accepted abbreviated display the structure and uniformity of idealised LB films.notation for a columnar mesophase and has replaced the pre- Despite the structural control oVered by the LB technique and viously used D (discotic) nomenclature proposed in ref. 14. the intense research activity related to the possible applications 14 C. Destrade, P. Foucher, H. Gasparoux, N. H. Tinh A. M. Levelut of LB films over the past 15 years, the commercial exploitation and J. Malthete, Mol. Cryst. Liq. Cryst., 1984, 106, 121. of functional LB films composed of Pcs is unlikely. This is 15 A. S. Cherodian, A. N. Davies, R. M. Richardson, M. J. Cook, N. B. McKeown, A. J. Thomson, J. Feinjoo, G. Ungar and due to the prohibitively slow speed of deposition and the small K. J. Harrison, Mol. Cryst. Liq. Cryst., 1991, 196, 103. area of substrate that can be covered. Self-ordering spin- 16 P. Weber, D. Guillon and A. Skoulios, Liq. Cryst., 1991, 9, 369; coated films, such as described above, oVer a rapidly fabricated A. N. Cammidge, M. J. Cook, S. D. Haslam, R. M. Richardson alternative. and K. J. Harrison, Liq. Cryst., 1993, 14, 1847; N. Spielberg, M. Sarkar, Z. Lutz, R. Poupko, J. Billard and H. Zimmerson, Liq. We thank the EPSRC for financial support (G.J.C.), provision Cryst., 1993, 15, 311. 17 T. Komatsu, K. Ohta, T.Watanabe, H. Ikemoto, T. Fujimoto and of studentships (K.E.T., A.S.S.T.) and for allocation of beam I. Yamamoto, J. Mater. Chem., 1994, 4, 537. time at Daresbury (S.R.S.). 18 K. E. Treacher, G. J. Clarkson and N. B. McKeown, Liq. Cryst., 1995, 19, 887. 19 M. Brewis, G. J. Clarkson, A. M. Holder and N. B. McKeown, References Chem. Commun, 1998, 969. 1 (a) N. B. McKeown, Phthalocyanine Materials: Synthesis, 20 M. J. Schtick, Nonionic Surfactants: Physical Chemistry, Marcel Structure and Function, Cambridge University Press, Cambridge, Dekker, New York, 1987. 1998; (b) C. C. LeznoV and A. B. P. Lever, Phthalocyanines: 21 T. Kunitake, Angew. Chem., Int. Ed. Engl., 1992, 31, 709. Properties and Applications, vols. 1–4, VCH, New York, 1989, 1993, 1993, 1997; (c) H. Schultz, H. Lehmann, M. Rein and Paper 8/05557B 2378 J. Mater. Chem., 1998, 8(11), 2371–2378