Recognition of aqueous flavin mononucleotide on the surface of binary monolayers of guanidinium and melamine amphiphiles Katsuhiko Ariga, Ayumi Kamino, Hiroshi Koyano and Toyoki Kunitake*† Supermolecules Project, JST (Former JRDC), Kurume Research Park, 2432 Aikawa, Kurume 839, Japan Recognition of aqueous flavin mononucleotide (FMN) on the surface of binary monolayers of guanidinium amphiphiles (monoalkyl derivative, C18Gua, or dialkyl derivative, 2C18Gua) and the melamine amphiphile (2C18mela-NN) has been investigated by p–A isotherms, FTIR spectroscopy, and XPS measurements.p–A Isotherms and FTIR spectra of C18Gua–2C18mela-NN (151) monolayers show that there is no direct hydrogen bonding and/or coulombic interactions between C18Gua and 2C18mela-NN on pure water and that the C18Gua component is dissolved into the subphase upon compression.In contrast, the presence of aqueous FMN prevented C18Gua molecules from dissolving into the subphase. Maximum condensation was observed at a 151 ratio in C18Gua–2C18mela-NN mixed monolayers on aqueous FMN. XPS analyses revealed that one FMN molecule was bound to one C18Gua–2C18mela-NN (151) unit and binding was saturated at 5×10-6 mol dm-3 FMN.Peak shifts observed in FTIR spectra indicated that the isoalloxiazine ring in FMN formed hydrogen bonds with 2C18mela-NN. These results support a model that the isoalloxazine and phosphate functions in FMN are bound via hydrogen bonding to melamine in 2C18mela-NN and guanidinium in C18Gua, respectively. Similar binding behaviour of FMN was observed for mixed monolayers of 2C18Gua–2C18mela-NN.Hydrogen bonding is highly directive unlike other secondary from AFM observation that a regular pattern of monolayer components was formed upon binding of FAD to a valence forces and plays an important role in molecular design of receptor–guest systems with high specificity.1–4 It has been C18Gua–2C18Oro mixed monolayer.23 It is expected that one can make various patterns through combinations of dierent believed that molecular recognition via hydrogen bonding is dicult in polar media such as water due to competition from amphiphiles and aqueous guests.However, diculties in preparing desirable recognition sys- the latter, and most eective designs have been carried out in non-aqueous media. Thermodynamic analyses by Williams tems are still sometimes encountered.One of the major di- culties is undesirable interactions among component et al.5 and Adrian and Wilcox6 suggested that a molecular design to induce entropic gain upon releasing bound water amphiphiles. For example, recognition of aqueous AMP by a mixed monolayer of C18Gua and 2C18Oro [Fig. 1(A)] is not would compensate an enthalpic disadvantage in polar media.This disadvantage may be avoided by creation of a local non- ecient,22 because ion pairing between guanidinium and orotate competes with their binding to the guest.24 Two-dimen- aqueous environment in water. Nowick et al.7 and Bonar- Law8 incorporated recognition sites in the hydrophobic core sional crystallization of an azobenzene-type monolayer of C10AzoAT sometimes disturbs the formation of a desirable of micelles, while Komiyama et al.9 immobilized hydrogen bonding sites in a water-insoluble polymer.recognition site.25 In order to develop mixed monolayer systems which can recognize various kinds of aqueous guests, we Unlike these approaches, we have studied the aqueous phase near a hydrophobic phase, i.e., interfaces with water.Our have to establish a strategy to avoid unfavourable interactions within monolayers. quantum chemical calculation based on a multidielectric model revealed that hydrogen bonding was enhanced at the air/water Here, we demonstrate recognition of flavin mononucleotide (FMN) by mixed monolayers of guanidinium amphiphiles interface, since electronic properties of molecules located in water close to the hydrophobic phase are aected by the low (monoalkyl derivative, C18Gua, and dialkyl derivative, 2C18Gua) and a melamine amphiphile (2C18mela-NN) dielectric medium, thus the molecules behave as if they are in a less polar medium.10 We have also demonstrated experimen- [Fig. 1(B), (C)]. The following aspects were considered to achieve eective recognition: (1) a guanidinium component tally that molecular recognition through hydrogen bonding is eective at the air/water interface. Nucleotides,11 nucleic acid was selected, as the strong interaction between guanidinium and phosphate11a would enhance the recognition eciency; bases,12 sugars,13 amino acids14 and peptides15 dissolved in the aqueous subphase are eectively bound by receptor mono- (2) the N,N-disubstituted 2C18mela-NN molecule has only one face of the three-point recognition site of the melamine ring. layers.Molecular recognition at the air/water interface has been recently reported by other groups as well.16–20 This new We thus expect a 151 recognition in contrast to network formation observed for N,N¾-disubstituted melamines;26 (3) ion finding is also applicable to microscopic interfaces formed by micelles and bilayers dispersed in bulk water.21 pairing can be avoided between guanidinium and melamine under normal conditions.These monolayer interfaces can be composed of a variety of amphiphile molecules, thus creating varied recognition sites. We already reported that a ternary monolayer of guanidinium Results and Discussion (C18Gua), diaminotriazine (C10AzoAT) and orotate (2C18Oro) recognizes flavin adenine dinucleotide (FAD) [Fig. 1(A)].22 In Monolayer behaviour of mixtures of guanidinium and melamine this system, guanidinium, diaminotriazine and orotate func- amphiphiles on water tions in monolayers are bound to phosphate, isoalloxazine and The behaviour of mixed monolayers of C18Gua and 2C18mela- adenosine units in FAD, respectively.It was also confirmed NN was examined on pure water. The monoalkyl guanidinium amphiphile C18Gua is relatively hydrophilic forming only an † Permanent address: Faculty of Engineering, Kyushu University, 1 Hakozaki, Higashiku, Fukuoka 812, Japan. unstable monolayer which is readily dissolved into water upon J. Mater. Chem., 1997, 7(7), 1155–1161 1155Fig. 1 Multisite binding of mixed monolayers with complementary aqueous guests: A, mixed monolayer of C10AzoAT, C18Gua and 2C18Oro on FAD; B, mixed monolayer of 2C18mela-NN and C18Gua on FMN; C, mixed monolayer of 2C18M and 2C18Gua monolayers on FMN compression.24 Therefore, p–A isotherms of the C18Gua mono- component in the mixed monolayer. The isotherm of the layer have a poor reproducibility on pure water and the 2C18mela-NN monolayer displays only a condensed phase molecular area is smaller than the cross-sectional area of the with a limiting area of 0.44 nm2, indicating formation of a well monoalkyl chain.packed monolayer. The isotherm of C18Gua–2C18mela-NN p–A Isotherms of 2C18mela-NN and C18Gua–2C18mela-NN (151) monolayer is similar in shape to that of the 2C18mela- (151) monolayers on pure water are shown in Fig. 2(A). Since NN single-component monolayer. The dierence in the mol- the molecular areas are normalized by the number of 2C18mela- ecular area between the two isotherms is only 0.05 nm2, and NN molecules, the dierence in molecular area between the is much smaller than the cross-section of one monoalkyl chain.two isotherms represents the area occupied by the C18Gua The area of a mixed monolayer compressed at 30 mN m-1 was observed to decrease with time. These results strongly suggest that C18Gua is dissolved in water upon compression in spite of the presence of the 2C18mela-NN component. The monolayers on pure water were transferred onto golddeposited glass plates and their FTIR spectra were measured in the reflection–absorption mode (RAIRS).Fig. 3 shows spectra of a cast film of C18Gua and LB films of 2C18mela-NN and C18Gua–2C18mela-NN (151). The cast film is a substitute for an LB film of the C18Gua component, since LB transfer of the C18Gua monolayer from pure water was dicult. In the spectrum of C18Gua [Fig. 3(A)], n(CNN) and d(NH) peaks of the guanidinium moiety are seen at 1680 and 1628 cm-1, respectively.27 The triazine n(CNN) peak at 1579 cm-1 and broad d(NH) peak at 1600–1700 cm-1 are observed in the spectrum of 2C18MLB film [Fig. 3(B)].28 The spectrum of the C18Gua–2C18mela-NN (151) LB film [Fig. 3(C)] is essentially identical to that of the single-component 2C18mela-NN LB film. The former spectrum does not contain any feature of the C18Gua component.These spectral characteristics clearly reveal dissolution of the C18Gua component into subphase during compression. These results also indicate the absence of specific (hydrogen bonding and/or coulombic) interaction between C18Gua and Fig. 2 p–A Isotherms of (1) 2C18mela-NN and (2) C18Gua–2C18mela- 2C18mela-NN. In the case of a mixed monolayer of C18Gua NN (151) monolayers at 20 °C: A, on pure water; B, on 1×10-5 mol and 2C18Oro, guanidinium and orotate functions form a stable dm-3 of aqueous FMN.Molecular area was calculated on the basis of the number of 2C18mela-NN molecules. 151 ion pair with specific peak shifts in the FTIR spectrum.24 1156 J. Mater. Chem., 1997, 7(7), 1155–1161Fig. 3 FTIR spectra of multilayer films (5 Y-type films) on goldcoated glass plates: A, C18Gua cast film; B, 2C18mela-NN LB film transferred from pure water; C, C18Gua–2C18mela-NN (151) LB film transferred from pure water Thus, guanidinium and melamine functions should act on the FMN guest without mutual interference. Fig. 4 (A) p–A Isotherm of mixed monolayers of C18Gua and 2C18mela-NN at 20 °C: a, C18Gua 100.0%; b, 79.9%; c, 59.9%; d, p–A Isotherms of mixed monolayers of C18Gua–2C18mela-NN 39.9%; e, 19.9%; f, 0.0%.(B) Plots of normalized deviation against on aqueous FMN the fraction of C18Gua at 5, 10, 15, 20, 25, 30, 35 and 40 mN m-1 We subsequently investigated the interaction of aqueous FMN (from the bottom). with the mixed monolayer. In remarkable contrast with the preceding results, a monolayer of C18Gua becomes stable on upon mixing.However, it is more likely that condensation of 1×10-5 mol dm-3 FMN and gives satisfactory reproducibility the mixed monolayer via FMN binding is most pronounced in its p–A isotherm. Apparently, binding of FMN to the for the equimolar monolayer. As the surface pressure increases, monolayer prevents the guanidinium component from disthe condensation eect is suppressed because of increased solution into subphase, as also observed with aqueous molecular packing at all the mixing ratios.However, binding FAD.24 Fig. 2(B) shows isotherms of 2C18mela-NN and of FMN to the monolayer proceeds even at high surface C18Gua–2C18mela-NN (151) monolayers on 1×10-5 mol pressures, as confirmed by XPS and FTIR results as dis- dm-3 FMN.Again, molecular areas are normalized by the cussed below. number of 2C18mela-NN molecules. The dierence in the molecular area between two isotherms is 0.20–0.25 nm2, in Binding analysis of aqueous FMN to mixed monolayers of reasonable agreement with the cross-sectional area of mono- C18Gua–2C18mela-NN by XPS measurements alkyl C18Gua. In order to investigate the stoichiometry of interacting Quantitative analysis of FMN binding was conducted by XPS components, p–A isotherms of the mixed monolayer were measurements.The amount of FMN bound to monolayers measured in varying mixing ratios on 1×10-5 mol dm-3 was determined from the elemental ratio of phosphorus and FMN. The data were normalised by the total number of nitrogen in XPS measurement of the transferred monolayer amphiphile molecules used and are shown in Fig. 4(A). (Table 1). The FMN/C18Gua ratio is close to unity for a Deviations of the observed molecular area from that of an C18Gua monolayer, indicating that one FMN molecule is ideal mixture were calculated according to the following equa- bound to each C18Gua molecule; the guanidinium group is tions,29 stoichiometrically bound to a phosphate unit.Although weak interactions to carbonyl and/or the lone pair on nitrogen in Aideal=xAa+(1-x)Ab (1) the isoalloxazine unit of FMN are also conceivable,11b,17b the Normalized deviation=(Aobs-Aideal)/Aideal (2) equimolar binding ratio observed strongly suggests that the binding occurs between guanidinium and phosphate and that where Aa, Ab, Aideal, Aobs, and x represent the molecular area of component a, molecular area of component b, mean molecu- the other possibilities are unlikely.The ratio of FMN bound to single-component 2C18mela- lar area for an ideal mixture, observed mean molecular area, and mole fraction of component a, respectively. Normalized NN monolayer is 0.44 under the same conditions. The binding constant reported for aqueous cyclic imide (thymine) and a deviations obtained with eqn.(2) are plotted in Fig. 4(B). At low surface pressures, the negative deviation (condensation diaminotriazine monolayer is only 2×102 dm3 mol-1,12a while the constant between aqueous phosphate(AMP) and a guanidi- eect) is maximized at an equimolar mixing ratio. This result might be considered to originate from an entropic contribution nium monolayer is 3×106 dm3 mol-1.11a The hydrogen bond- J.Mater. Chem., 1997, 7(7), 1155–1161 1157Table 1 Binding of FMN to monolayers as determined by XPSa amphiphile unit [FMN]/mmol dm-3 P (%) N (%) Rb C18Gua 0.01 1.52 9.92 1.07 2C18mela-NN 0.01 0.50 11.28 0.44 C18Gua–2C18mela-NN (151) 0.00 0.00 11.05 0.00 C18Gua–2C18mela-NN (151) 0.0001 0.55 11.55 0.62 C18Gua–2C18mela-NN (151) 0.005 0.90 11.04 1.06 C18Gua–2C18mela-NN (151) 0.01 0.93 10.96 1.10 C18Gua–2C18mela-NN (151) 0.10 0.94 10.93 1.12 2C18Gua–2C18mela-NN (151) 0.01 0.76 10.10 1.06 aLB films (9 or 10 layers) were used for measurement.bR=Bound FMN/amphiphile. ing interactions between a neutral receptor and guest, e.g., 2C18mela-NN–isoalloxazine (FMN), is less ecient. The XPS results reveal that the binding ratio of FMN to C18Gua–2C18mela-NN (151) is close to unity at FMN concentrations >5×10-6 mol dm-3, consistent with the binding motif of Fig. 1(B) where one FMN molecule simultaneously binds to one guanidinium and one melamine. Since the binding eciency is ca. 50% at 10-7 mol dm-3 FMN and is saturated at 5×10-6 mol dm-3 FMN, the binding constant is estimated to be in the range of 107 dm3 mol-1.FTIR examination of the receptor–guest interaction The mode of the receptor–guest interaction was studied by FT RAIRS spectroscopy of monolayer receptors transferred onto a gold-deposited plate. IR spectral changes caused by FMN binding were characterized separately for the two functional components of the receptor monolayer (Fig. 5 and 6).Fig. 5 shows IR spectral characteristics of C18Gua and FMN in the region 1200–1900 cm-1. According to the literature,30,31 the peaks observed for an FMN cast film [Fig. 5(C)] are assigned as follows: n(C4NO) at 1729, n(C2NO) at 1681; n(CNN) at 1579 and n(CNN) at 1550 cm-1. The spectrum of a C18Gua LB film transferred from 1×10-5 mmol dm-3 of aqueous FMN [Fig. 5(B)] is basically a superimposition of the two components, although some peak broadening by overlapping is seen in the 1600–1700 cm-1 region. The presence of FMN Fig. 6 FTIR spectra of multilayer films (5 Y-type films) on goldcoated glass plates: A, 2C18mela-NN LB film transferred from pure water;B, 2C18mela-NN LB film transferred from aqueous 1×10-5 mol dm-3 FMN; C, FMN cast film peaks indicates the binding of FMN to the C18Gua monolayer.The absence of significant shifts of CNO peaks implies that the guanidinium unit in the monolayer is not bound to the isoalloxiazine ring of FMN. Fig. 6 summarizes similar FTIR data for the 2C18mela-NN monolayer. Comparison of IR spectra of 2C18mela-NN LB films transferred from pure water [Fig. 6(A)] and from 1×10-5 mol dm-3 aqueous FMN [Fig. 6(B)] reveals that the latter spectrum shows new peaks at 1676, 1620 and 1551 cm-1 which can be assigned to n(C4NO), n(C2NO) and a n(CNN) stretch, respectively. The former two peaks show shifts to lower wavenumbers relative to the corresponding peaks of the FMN cast film. This suggests that 2C18mela-NN binds to isoalloxazine of FMN via hydrogen bonding. Similar spectral shifts were reported by Kyogoku et al.32 for hydrogen bonding between FMN and adenine derivatives.Fig. 7 shows spectra of a C18Gua–2C18mela-NN (151) LB film transferred from aqueous FMNat dierent concentrations. The n(CNO) peaks of isoalloxazine are shifted to 1676 and 1626 cm-1, indicating that FMN is bound to the mixed monolayer through hydrogen bonding. The peak at 1580 cm-1 is an overlapped peak of 2C18mela-NN and FMN, while that at 1550 cm-1 arises from bound FMN only.Therefore, the intensity of the latter peak is relatively weak at 1×10-7 mol Fig. 5 FTIR spectra of multilayer films (5 Y-type films) on gold- dm-3 FMN where the ratio of bound FMN to amphiphile coated glass plates: A, C18Gua cast film; B, C18Gua LB film transferred from aqueous 1×10-5 mol dm-3 FMN; C, FMN cast film is low. 1158 J. Mater. Chem., 1997, 7(7), 1155–1161Fig. 7 FTIR spectra of the C18Gua–2C18mela-NN (151) LB films (5 Y-type films) transferred from aqueous FMN: A, 1×10-7 mol dm-3; B, 1×10-5 mol dm-3; C, 1×10-4 mol dm-3 The IR data are again consistent with the binding motif of Fig. 1(B), i.e., one FMN molecule is bound to one guanidinium and one melamine with formation of a guanidinium–phosphate Fig. 8 (A) p–A Isotherms of mixed monolayers of 2C18Gua and pair and isoalloxazine–melamine hydrogen bonding. 2C18mela-NN at 20°C: a, 2C18Gua 0.0%; b, 19.9%; c, 40.3%; d, 60.3%; e, 79.9%; f, 100.0%. (B) Plots of normalized deviation against Binding of aqueous FMN with 2C18Gua–2C18mela-NN the fraction of C18Gua at 5 (#), 10 ($), 15 ('), 20 (+), 25 (1), 30 monolayers (#), and 35 ($) mN m-1.We conducted a similar investigation by using a dialkyl guanidinium amphiphile, 2C18Gua. p–A Isotherms of 2C18Gua–2C18mela-NN monolayers on 1×10-5 mol dm-3 aqueous FMN are shown in Fig. 8(A). Normalized deviations of molecular area calculated using eqn. (1) and (2) are plotted in Fig. 8(B) as a function of the fraction of 2C18Gua. p–A Isotherms show a condensed phase alone, and condensation eects are not significant at any mixing ratio.Collapse pressures are minimized at a monolayer composition close to equimolar mixing [curve (c) for 40.3% 2C18Gua and curve (d) for 60.3% of 2C18Gua]. Fig. 9 shows FTIR spectra of a 2C18Gua LB film transferred from pure water [Fig. 9(A)], a 2C18Gua LB film transferred from 1×10-5 mol dm-3 aqueous FMN [Fig. 9(B)], and 2C18Gua–2C18mela-NN (151) LB film transferred from 1×10-5 mol dm-3 aqueous FMN [Fig. 9(C)]. The latter two spectra show evidence of FMN binding, i.e., n(CNN) peaks of FMN at 1579 and 1549 cm-1 and peak broadening in the 1600–1700 cm-1 region due to overlapped n(CNO) peaks of FMN. Therefore, FMN is bound to both the 2C18Gua monolayer and the 2C18Gua–2C18mela-NN (151) monolayer.Binding of FMN is also confirmed by XPS (bottom row in Table 1). The observed elemental ratio indicates the presence of one FMN molecule per 2C18Gua–2C18mela-NN (151) unit and the spectroscopic data are in accord with the binding motif shown in Fig. 1(C). Conclusion Fig. 9 FTIR spectra of multilayer films (5 Y-type films) on goldcoated glass plates: A, 2C18Gua LB film transferred from pure water; Binding of aqueous FMN to guanidinium–melamine binary B, 2C18Gua LB film transferred from 1×10-5 mol dm-3 of aqueous monolayers has been investigated.The monolayer behaviour FMN; C, 2C18Gua–2C18mela-NN (151) LB film transferred from 1×10-5 mol dm-3 of aqueous FMN on pure water shows the absence of specific functional inter- J. Mater. Chem., 1997, 7(7), 1155–1161 1159actions between the two kinds of amphiphiles.Both amphi- subphase temperature was kept at 20±0.2°C. The surface pressures were measured by a Wilhelmy plate, which was philes are basic and cannot form a strongly interacting complex between themselves. FTIR data suggests the presence of hydro- calibrated with the transition pressure of an octadecanoic acid monolayer.gen bonding between the melamine amphiphile and the isoalloxazine unit of FMN. Quantitative analysis by XPS LB films were transferred onto gold-deposited glass plates for reflection–absorption FTIR spectroscopy. The substrate measurements reveals that one FMN molecule binds to one guanidinium molecule and one melamine molecule with a was prepared as follows. A slide glass (pre-cleaned, 176×26×1 mm, Iwaki Glass) was immersed in a detergent binding constant of ca. 107 dm3 mol-1. This eective binding originates owing to the absence of competitive amphiphile– solution overnight (Dsn 90, Bokusui Brown). The glass was washed with a large excess of ion-exchanged water to remove amphiphile interactions. Multisite binding in a mixed monolayer would produce a the detergent completely, and subjected to sonication in fresh ion-exchanged water several times.After the glass was dried regular molecular arrangement in a two-dimensional plane as shown in Fig. 1. In fact, AFM observations revealed that a in vacuo for over 1 h, thin layers of chromium and gold were consecutively formed by the vapour-deposition method mixed monolayer of C18Gua and 2C18Oro on aqueous FMN formed a regular two-dimensional molecular pattern.23 A large (1000 A° Au/50 A° Cr/slide glass) with a vapour-deposition apparatus VPC-260 (ULVAC Kyushu).variety of molecular patterns can be created by appropriate combinations of receptor and guest molecules. For example, LB transfer was carried out with a FSD-21 instrument (USI System, Fukuoka) by the vertical dipping method.Monolayers system A, B, and C of Fig. 1 would form dierent patterns. However, mutual interactions in monolayers sometimes disturb were transferred on Au-coated glass plates at 30 mN m-1 with dipping speeds of 20 mm min-1 (downstroke) and 5 mm min-1 guest binding. A mixed monolayer of C18Gua–2C18Oro (151) does not bind AMP eciently because of ion pairing between (upstroke).Transfer of 2C18Gua–2C18mela-NN (151) monolayer from aqueous FMN was conducted at 20 mN m-1 the two components and shows that mutual interaction between receptor components can seriously limit the pat- because of its low collapse pressure. Transfer ratios were almost unity and Y-type transfer was used. terning.24 In order to obtain designed molecular patterns, we have to avoid such interactions and the present system of guanidinium, melamine and FMN meets these conditions.Characterization of LB films Further development of suitable recognition systems will lead FTIR spectra (reflection–absorption mode) were measured to an increased variety of two-dimensional molecular patterns. with LB films (5 Y-type films) transferred onto gold-deposited glass plates with a Nicolet 710 FTIR spectrometer.Experimental X-Ray photoelectron spectra (XPS) were measured for the LB films (5 Y-type films) on Au/Cr/glass with a Perkin-Elmer Materials PHI 5300 ESCA instrument using an Mg-Ka X-ray source (300W). Repeated scans over the same surface region at a Flavine mononucleotide monosodium salt (FMN) was comtake- o angle of 45° gave reproducible spectra.The elemental mercially supplied (Wako Pure Chem.). The water used for composition was obtained by dividing the observed peak area the subphase was deionized and doubly distilled using a by the intrinsic sensitivity factor of each element. Nanopure II-4P and Glass Still D44 System (Barnstead). Spectroscopic grade benzene and ethanol (Wako Pure Chem.) were used as spreading solvents.Gold (99.999%) and chro- References mium (99.99%) used for the surface modification of solid substrates were purchased from Soekawa Chemicals. Synthetic 1 (a) J. Rebek Jr. and D. Nemeth, J. Am. Chem. Soc., 1986, 108, 5637; methods for 2C18Gua and C18Gua are described elsewhere.33 (b) J. Rebek Jr., Acc. Chem. Res., 1990, 23, 399. 2 (a) S-K. Chang, D. Van Engen, E.Fan and A. D. Hamilton, J. Am. The melamine amphiphile, 2C18mela-NN, was synthesized Chem. Soc., 1991, 113, 7640; (b) A. D. Hamilton and D. Van Engen, as follows. J. Am. Chem. Soc., 1987, 109, 5035. 3 (a) Y. Aoyama, Y. Tanaka, H. Toi and H. Ogoshi, J. Am. Chem. 2,4-Diamino-6-(dioctadecylamino) triazine (2C18mela-NN) Soc., 1988, 110, 634; (b) Y. Aoyama, Y. Tanaka and S.Sugahara, J. Am. Chem. Soc., 1989, 111, 5397. A mixture of 2,4-diamino-6-chlorotriazine (290 mg, 4 (a) J-M. Lehn, Pure Appl. Chem., 1994, 66, 1961; (b) K. C. Russell, 1.99 mmol), dioctadecylamine21 (1.04 mg, 1.99 mmol) and E. Leize, A. Van Dorsselaer and J-M. Lehn, Angew. Chem., Int. Ed. KHCO3 (200 mg, 1.99 mmol) in 1,4-dioxane (20 cm3) was Engl., 1995, 34, 209; (c) A. Marsh, E.G. Nolen, K. M. Gardinier and J-M. Lehn, T etrahedron L ett., 1994, 35, 397. refluxed for 6 h. Water (50 cm3) was added to the mixture and 5 (a) A. J. Doig and D. H. Williams, J. Am. Chem. Soc., 1992, 14, 338; the insoluble material was collected by filtration. The solid (b) D. H. Williams, J. P. L. Cox, A. J. Doig, M. Gardner, collected on the filter was washed with water and dried to give U.Gerhard, P. T. Kaye, A. R. Lal, I. A. Nicholls, C. J. Salter and a slightly yellow powder. This was chromatographed on SiO2 R. C. Mitchell, J. Am. Chem. Soc., 1991, 113, 7020. (200 g; CH2Cl2–MeOH, 1051). The product fractions were 6 (a) J. C. Adrian and C. S. Wilcox, J. Am. Chem. Soc., 1991, 113, 678; collected and concentrated to give a solid. This was recrys- (b) 1992, 114, 1398. 7 (a) J. S. Nowick and J. S. Chen, J. Am. Chem. Soc., 1992, 114, 1107; tallized from EtOH–MeOH to give 2C18mela-NN (458 mg, (b) J. S. Nowick, J. S. Chen and G. Noronha, J. Am. Chem. Soc., 36%) as a colourless solid. Mp, 49.7–55.8°C; TLC Rf 0.49 1993, 115, 7636; (c) J. S. Nowick, T. Cao and G. Noronha, J. Am. (CH2Cl2–methanol, 1051); 1H NMR (CDCl3, 300 MHz) d 0.88 Chem. Soc., 1994, 116, 3285.(t, 6H, J=6.6 Hz, 2 CH3), 1.2–1.4 (m, 60H, 30 CH2), 1.4–1.6 8 R. P. Bonar-Law, J. Am. Chem. Soc., 1995, 117, 12397. (m, 4H, 2 CH2CH2N), 3.44 (t, 4H, J=7.6 Hz, 2 CH2N), 5.23 9 H. Asanuma, S. Gotoh, T. Ban and M. Komiyama, Chem. L ett., (br s, 4H, 2 NH2). Anal. Calc. for C39H78N6·0.5H2O: C, 73.18; 1996, 681. 10 M. Sakurai, H. Tamagawa, T. Furuki, Y. Inoue, K. Ariga and H, 12.44; N, 13.13.Found: C, 73.28; H, 12.41; N, 12.83%. T. Kunitake, Chem. L ett., 1995, 1001. 11 (a) D. Y. Sasaki, K. Kurihara and T. Kunitake, J. Am. Chem. Soc., p–A Isotherm measurement and LB transfer 1991, 113, 9685; (b) 1992, 114, 10994; (c) D. Y. Sasaki, M. Yanagi, K. Kurihara and T. Kunitake, T hin Solid Films, 1992, 210/211, p–A isotherms were measured with a computer-controlled film 776.balance system FSD-50 (USI System, Fukuoka). A mixture of 12 (a) K. Kurihara, K. Ohto, Y. Honda and T. Kunitake, J. Am. Chem. benzene–ethanol (80520, v/v) was used as a spreading solvent. Soc., 1991, 113, 5077; (b) T. Kawahara, K. Kurihara and Compression was started about 10 min after spreading at a T. Kunitake, Chem. L ett., 1992, 1839. 13 (a) K. Kurihara, K.Ohto, Y. Tanaka, Y. Aoyama and T. Kunitake, rate of 0.2 mm s-1 (or 20 mm2 s-1 based on area). The 1160 J. Mater. Chem., 1997, 7(7), 1155–1161J. Am. Chem. Soc., 1991, 113, 444; (b) K. Kurihara, K. Ohto, K. Taguchi, A. Kamino, H. Koyano and T. Kunitake, L angmuir, 1997, 13, 519. Y. Tanaka, Y. Aoyama and T. Kunitake, T hin Solid Films, 1989, 179, 21. 24 A. Kamino, K.Taguchi, H. Koyano, K. Ariga and T. Kunitake, manuscript in preparation. 14 Y. Ikeura, K. Kurihara and T. Kunitake, J. Am. Chem. Soc., 1991, 113, 7342. 25 K. Taguchi, A. Kamino, H. Koyano, K. Ariga and T. Kunitake, manuscript in preparation. 15 (a) X. Cha, K. Ariga, M. Onda and T. Kunitake, J. Am. Chem. Soc., 1995, 117, 11833; (b) X. Cha, K. Ariga and T. Kunitake, J. Am. 26 H. Koyano, K.Yoshihara, K. Ariga, T. Kunitake, Y. Oishi, O. Kawano, M. Kuramori and K. Suehiro, Chem. Commun., 1996, Chem. Soc., 1996, 118, 73; (c) 9545. 16 H. Kitano and H. Ringsdorf, Bull. Chem. Soc. Jpn., 1985, 58, 2826. 1769. 27 L. J. Bellamy, T he Infrared Spectra of Complex Molecules, 17 (a) T. M. Bohanon, S. Dezinger, R. Fink, W. Paulus, H. Ringsdorf Chapman and Hall, London, 3rd edn., vol. 1, 1975. and M. Weck, Angew. Chem., Int. Ed. Engl., 1995, 34, 58; 28 M. Scoponi, E. Polo, F. Pradella, V. Bertolasi, V. Carassiti and (b) R. Ahuja, P-L. Caruso, D. Mo�bius, W. Paulus, H. Ringsdorf P. Goberti, J. Chem. Soc., Perkin T rans. 2, 1992, 1127. and G. Wildburg, Angew. Chem., Int. Ed. Engl., 1993, 32, 1033. 29 A. Kamino, K. Ariga, T. Kunitake, V. Birault, G. Pozzi, 18 X.-C. Chai, S.-G. Chen, Y.-L. Zhou, Y.-Y. Zhao, T.-J. Li and J.- Y. Nakatani and G. Ourisson, Colloids Surf., 1995, 103, 183. M. Lehn, Chin. J. Chem., 1995, 13, 385. 30 S. Suzuki, S. Isoda and M. Maeda, Jpn. J. Appl. Phys., 1989, 28, 19 M. Shimomura, O. Karthaus and K. Ijiro, Supramol. Sci., 1996, 1673. 3, 61. 31 V. I. Birss, A. S. Hinman, C. E. McGarvey and J. Segal, 20 Y. Ebara, K. Itakura and Y. Okahata, L angmuir, 1996, 12, 5165. Electrochim. Acta, 1994, 39, 2449. 21 M. Onda, K. Yoshihara, H. Koyano, K. Ariga and T. Kunitake, 32 Y. Kyogoku and B. S. Yu, Bull. Chem. Soc. Jpn., 1969, 42, 1387. J. Am. Chem. Soc., 1996, 118, 8524. 33 A. Kamino, H. Koyano, K. Ariga and T. Kunitake, Bull. Chem. 22 K. Taguchi, K. Ariga and T. Kunitake, Chem. L ett., 1995, 701. Soc. Jpn., 1996, 69, 3619. 23 (a) Y. Oishi, Y. Torii, M. Kuramori, K. Suehiro, K. Ariga, K. Taguchi, A. Kamino and T. Kunitake, Chem. L ett., 1996, 411; (b) Y. Oishi, Y. Torii, T. Kato, M. Kuramori, K. Suehiro, K. Ariga, Paper 7/00081B; Received 3rd January, 1997 J. Mater. Chem., 1997, 7(7), 1155–1161 11