Nanometric dendritic macromolecules: stepwise assembly by double (2,2¾56¾,2-terpyridine)ruthenium(I ) connectivity George R. Newkome* and Enfei He Center forMolecular Design and Recognition, University of South Florida, T ampa, Florida 33620, USA The construction of nanometric, dendritic macromolecules by bis(2,2¾56¾,2-terpyridine)ruthenium(II) connectivity is investigated. The assembly methodology, which incorporates both the control of metal complexation sites and degree of flexibility within the linkages, has been demonstrated.Interest in specifically assembled, dendritic nanostructures has saturated aqueous NaHCO3 solution was carefully added, then the solvent was removed in vacuo to aord a white solid, which continued to escalate over the past decade1 and will continue to do so due to the anticipation of their novel properties.was extracted with absolute EtOH (3×100 cm3). The extract was concentrated in vacuo to give tetraol 4, as a colourless oil. Dendritic systems which incorporate metal centres are either of a random nature by simple molecular inclusion within the (8.26 g, 95%) (Found: C, 55.69; H, 9.61. C17H36O8 requires C, 55.42; H, 9.85%); 1H NMR (MeOD), d 1.78 (m, 2H, macrostructure,2 or at a specific predetermined binding locus3 either within the assembly or on its surface.Such metallo- CH2CH2OH), 3.38 (s, 2H, CH2O), 3.55 (t, J 5.0 Hz, 2H, OCH2), 3.69 (t, J 5.1 Hz, 2H, CH2OH); 13C NMR (MeOD), macroassemblies aord entrance to materials capable of novel magnetic, electronic, photooptical or catalytic properties.As a d 31.8 (CH2CH2OH), 44.9 (Cquat), 60.5 (CH2OH), 69.7 (OCH2 ), 70.7 (CH2O); IR (neat), 3364, 2948, 2879, 1493, 1424, 1363, prelude to the construction process, we previously reported4–6 the use of bis(2,2¾56¾,2-terpyridine)ruthenium(II) (herein 1109 cm-1. denoted by [—<Ru>—]), as the mode of connectivity, in order to combine preconstructed, pseudo-spherical dendritic Tetrakis{5-[4¾-oxa-(2,2¾56¾,2-terpyridinyl )]-2- fragments in a predetermined way.Such connectivity permitted oxapentyl}methane 5 the analysis of the final product by the easy quantification of To a suspension of powdered KOH (1.10 g) in dry Me2SO the metal centre(s) by simple electrochemical procedures. This (15 cm3), was added tetraol 4 (600 mg, 1.63 mmol) in Me2SO type of connectivity (i.e., incorporation of multiple centres) (5 cm3).The suspension was heated to 60°C for 30 min, then gave rise to the dodecaruthenium complex4 1 and the single 4¾-chloro-2,2¾56¾,2-terpyridine9 (4¾-Cl-tpy; 1.92 g, 4.4 equiv.) metal centre aorded the bisdendrimer5 2 (Fig. 1); these rep- was added. After 24 h at 60°C, the mixture was cooled and resent our initial approaches to the specific assembly of discrete poured into cold water (300 cm3).The resultant white solid dendritic networks by the connection of established constructs. was filtered, washed with water, and dried in vacuo to give a We herein describe the use of two metal centres per appendage o-white solid, which was column chromatographed eluting [—<Ru>—(×)—<Ru>—] for attachment to a four-direc- with 15% EtOAc in CH2Cl2 to aord 5, as a white solid tional core; this assembly methodology incorporates (i) pos- (1.65 g, 78%), mp 161–164 °C (Found: C, 71.70; H, 5.57; N, itional control over the metal complexation sites and (ii) a 12.78; C77H72N12O8 requires C, 71.50; H, 5.61; N, 12.99%); 1H variable flexibility within the linkages (×) between those con- NMR, d 1.98 (m, 8H, J 5.6 Hz, OCH2CH2 ), 3.42 (s, 8H,CH2O), nectivity sites. 3.52 (t, 8H, J 5.6 Hz, OCH2), 4.18 (t, 8H, J 5.6 Hz, OCH2CH2CH2 ), 7.24 (t, 8H, J 5.2 Hz, H5,5), 7.74 (t, 8H, Experimental J 7.6 Hz, H4,4), 7.94 (s, 8H, H3¾,5¾), 8.54 (d, 8H, J 7.9 Hz, H3,3), 8.62 (d, 8H, J 4.7 Hz, H6,6); 13C NMR, d 29.4 Equipment and materials (OCH2CH2), 45.6 (Cquat), 65.2 (OCH2CH2CH2), 67.6 (OCH2 ), 69.9 (CH2O), 107.5 (C5,5), 121.3 (C4,4), 123.8 (C3,3), 136.7 Melting points are uncorrected and were measured on a Mel- (C3¾,5¾), 149.1 (C6,6), 156.2 (C2,2), 157.0 (C2¾,6¾), 167.2 (C4¾); IR Temp apparatus.All reactions were conducted under a nitrogen (KBr), 3063, 2933, 2876, 1609, 1593, 1570, 1493, 1440, 1416, atmosphere. 1H and 13C NMR spectra were recorded on a 1362, 1209, 1093, 801 cm-1.Bruker AC250 MHz spectrometer using CDCl3 as solvent, unless otherwise indicated, with Me4Si as the internal standard (d=0). IR spectra were recorded on a Perkin-Elmer 621 grating 4-[4¾-Oxa-(2,2¾56¾,2-terpyridinyl )]butanoic acid 6 IR spectrometer. UV–VIS spectra were recorded on a To a solution of 4-hydroxybutanoic acid (942 mg, 7.47 mmol) HP8452A diode array spectrophotometer.Elemental analyses and KOH (3 g) in dry Me2SO (30 cm3) at 60°C, was added were performed by M-H-W Laboratories, Phoenix, AZ. 4¾-Cl-tpy (2.00 g, 7.47 mmol). The mixture was maintained for All reagents were purchased from Aldrich. Column chroma- 36 h, then cooled to 25°C and poured into water (600 cm3) tography was performed using activated basic aluminium oxide aording a yellow transparent solution.The pH was adjusted (150 mesh, Brockmann I; Aldrich). to neutral by the addition of 10% aqueous HCl resulting in the formation of a white precipitate, which after standing for Tetrakis(5-hydroxy-2-oxapentyl )methane 4 at least 2 h, was filtered, washed with water, dried in vacuo to give the acid 6, as a white solid (2.15 g, 86%); mp 173–175 °C To a solution of 6,6-bis(carboxy-2-oxabutyl)-4,8-dioxaundecane- 1,11-dicarboxylic acid7 3 (10 g, 23.6 mmol) in dry THF (Found: C, 68.29; H, 5.29; N, 12.30.C19H17N3O3 requires C, 68.05; H, 5.11; N, 12.53%); 1H NMR, d 2.21 (m, 2H, J 6.0 Hz, (50 cm3) at 0°C, was added dropwise a BH3·THF8 solution (104 cm3, 4.4 equiv.) over 30min. The solution was stirred for OCH2CH2CH2 ), 2.57 (t, 2H, J 7.1 Hz, CH2CO2H), 4.31 (t, 2H, J 6.0 Hz, OCH2), 7.38 (td, 2H, J 4.9, 1.0 Hz, H5,5), 7.88 (td, 1 h, then warmed to 25°C and stirred for 3 h.Excess of a J. Mater. Chem., 1997, 7(7), 1237–1244 1237Fig. 1 Dendritic architectures incorporating (—<Ru>—) units 2H, J 7.8, 1.8 Hz, H4,4), 7.92 (s, 2H, H3¾,5¾), 8.61 (d, 2H, tert-butyl 4-[(2-tert-butoxycarbonyl)ethyl]-4-aminoheptanedicarboxylate 710 (2.48 g, 5.97 mmol) was added.The reaction J 7.9 Hz, H3,3), 8.67 (d, 2H, J 4.3 Hz, H6,6); 13C NMR, d 24.6 mixture was stirred for 36 h, after which the white precipitate (OCH2CH2CH2), 30.7 (CH2CO2H), 67.4 (OCH2), 107.6 (C5,5), was filtered o. The filtrate was concentrated in vacuo aording 121.9 (C4,4), 124.1 (C3,3), 137.3 (C3¾,5¾), 148.9 (C6,6), 156.1 a crude oil, which was dissolved in Et2O (200 cm3), washed (C2,2), 157.0 (C2¾,6¾), 167.2 (C4¾), 175.7 (CO2H); IR (KBr), 3063, with 10% aqueous Na2CO3 (2×100 cm3), brine (2×100 cm3), 2956, 2918, 2879, 1709, 1593, 1570, 1478, 1450, 1416, 1370, dried (MgSO4), and concentrated in vacuo to aord a solid, 1262, 1209, 1040, 801, 747 cm-1.which was recrystallized from cyclohexane (3.15 g, 72%); mp 146–149 °C (Found: C, 67.36; H, 7.51; N, 7.85.C41H56N4O8 N-{Tris[(2-tert-butoxycarbony)ethyl]methyl}[4¾-oxa- requires C, 67.19; H, 7.70; N, 7.64%); 1H NMR, d 1.42 (s, 27H, ( 2,2¾56¾,2-terpyridinyl )]butamide 8 CH3), 2.01 (t, 6H, J 8.2 Hz, CH2CO2), 2.23 (m, 8H, To a solution of acid 6 (2.0 g, 5.97 mmol) in dry DMF (30 cm3), CH2CH2CONH, CH2CH2CO2), 2.36 (t, 2H, J 7.1 Hz, were added dicyclohexylcarbodiimide (DCC; 1.23 g, CH2CONH), 4.28 (t, 2H, J 5.9 Hz, OCH2 ), 6.03 (s, 1H, NH), 5.97 mmol) and 1-hydroxybenzotriazole (1-HOBT; 806 mg, 7.32 (td, 2H, J 4.8, 1.8 Hz, H5,5), 7.84 (td, 2H, J 7.8, 1.7 Hz, H4,4), 8.01 (s, 2H, H3¾,5¾), 8.60 (d, 2H, J 8.0 Hz, H3,3), 8.68 (d, 5.97 mmol) at 25°C.This mixture was stirred for 1 h, then di- 1238 J.Mater. Chem., 1997, 7(7), 1237–1244Scheme 1 Reagents and conditions: i, BH3 ·THF, 1 h, 0°C, then 3 h, 25 °C; ii, 4¾-Cl-tpy, KOH, Me2SO, 24 h, 60 °C Scheme 2 Reagents and conditions: i, 4¾-Cl-tpy, KOH, Me2SO, 36 h, 60 °C; ii, DCC, 1-HOBT, DMF, 36 h, 25 °C; iii, RuCl3 3H2O, MeOH, 3 h,reflux J. Mater. Chem., 1997, 7(7), 1237–1244 1239Scheme 3 Reagents and conditions: i, 4¾-Cl-tpy, KOH, Me2SO, 36 h, 60°C; ii, 4-ethylmorpholine, MeOH, 2 h, reflux Scheme 4 Reagents and conditions: i, DCC, 1-HOBT, DMF, 48 h, 25 °C; ii, RuCl3 ·3H2O, MeOH, 6 h, reflux 1240 J.Mater. Chem., 1997, 7(7), 1237–1244Scheme 5 Reagents and conditions: i, 4-ethylmorpholine, MeOH–CHCl3, 4 h, reflux 2H, J 4.3 Hz, H6,6); 13C NMR, d 25.2 (CH2CH2CON), 28.2 (2×10 cm3) then dried in vacuo, yielding 9, as a yellow–brown solid (1.94 g, 76%); mp>202°C (decomp.); (Found C, 52.17; (CH3 ), 29.9 (CH2CO2), 30.2 (CH2CH2CO2), 33.6 (CH2CON), 57.6 (NHC), 67.4 (OCH2), 80.8 [C(CH3)3], 107.5 (C5,5), 121.4 H, 5.95; N, 6.06.C41H56Cl3N4O8Ru requires C, 52.37; H, 6.00; N, 5.96%); IR (KBr), 3340, 3071, 2987, 2940, 1732, 1670, 1609, (C4,4), 123.9 (C3,3), 136.9 (C3¾,5¾), 149.1 (C6,6), 156.2 (C2,2), 157.2 (C2¾,6¾), 167.2 (C4¾), 171.6 (CONH), 173.0 (CO2); IR 1555, 1471, 1370, 1224, 1160, 1047, 801 cm-1; UV–VIS, lmax= 232 (e=3.27×104), 278 (2.91×104), 312 (1.63×104), 402 (KBr), 3341, 3063, 3010, 2987, 2933, 1732, 1671, 1586, 1563, 1478, 1452, 1362, 1155, 793 cm-1.(9.32×103), 466 nm (3.73×103 dm3 mol-1 cm-1). 5-Aminopentyl 4¾-(2,2¾56¾,2-terpyridinyl ) ether 10 Ruthenium(III ) complex of N-{tris[(2-tertbutoxycarbony) ethyl]methyl}[4¾-oxa-(2,2¾56¾,2- To a suspension of powdered KOH (2.0 g) in dry Me2SO terpyridinyl )]butamide 9 (30 cm3), was added 5-aminopentan-1-ol (770 mg, 7.47 mmol).The suspension was stirred at 60°C for 30 min, then 4¾-Cl-tpy A solution of RuCl3·3H2O (709 mg, 2.71 mmol) and 8 (2.0 g, 2.71 mmol) in MeOH (50 cm3) was refluxed for 3 h.After (2.00g, 7.47 mmol) was added. The whole mixture was stirred at 60°C for an additional 36 h. After cooling to 25°C, the cooling, the yellow–brown precipitate was filtered, washed sequentially with MeOH (5 cm3), water (2×20 cm3) and Et2O mixture was poured into water (600 cm3), stirred, then allowed J. Mater. Chem., 1997, 7(7), 1237–1244 1241to set for 3 h.The precipitate was filtered, washed with water, (CONHCH2), 57.4 (CONHC), 67.4 (free tpy-OCH2,), 69.3 (OCH2), 71.0 (CH2O), 107.2 (free tpy C5,5), 111.1 (C5,5), 121.2 and dried in vacuo to give a crude product, which was column chromatographed eluting with 10% MeOH in CH2Cl2 to yield (free tpy C4,4), 123.9 (free tpy C3,3), 124.5 (C4,4), 127.8 (C3,3 ), 136.9 (free tpy C3¾,5¾), 137.7 (C3¾,5¾), 148.9 (free tpy C6,6), 10, as a light yellow solid (1.78 g, 71%); mp 104–106 °C (Found: C, 72.04; H, 6.46; N, 16.60.C20H22N4O requires C, 152.0 (C6,6), 153.7 (C2,2), 156.7, 156.8 (C2¾,6¾, free tpy C2,2), 158.0 (free tpy C2¾,6¾), 162.5 (CONHCH2), 165.9, 166.2, 166.8 71.83; H, 6.63; N, 16.75%); 1H NMR, d 1.49–1.55 (m, 6H, NH2, NCH2CH2CH2), 1.82 (m, 2H, CH2CH2O), 2.67 (t, 2H, (C4¾, free tpy C4¾), 172.1 (CONHC), 172.9 (CO2); IR (KBr), 3418, 3333, 3071, 2980, 2940, 2851, 1724, 1678, 1616, 1563, J 6.1 Hz, NCH2), 4.17 (t, 2H, J 6.2 Hz, CH2O), 7.29 (td, 2H, J 4.9, 1.6 Hz, H5,5), 7.78 (td, 2H, J 7.2, 1.4 Hz, H4,4), 8.01 (s, 1470, 1393, 1370, 1216, 1162, 847, 790, 754 cm-1; UV–VIS, lmax=244 (e=6.86×104), 270 (7.13×104), 304 (7.19×104), 2H, H3¾,5¾), 8.59 (d, 2H, J 7.9Hz, H3,3), 8.65 (d, 2H, J 4.4 Hz, H6,6); 13C NMR, d 23.2 (NCH2CH2CH2 ), 28.8 (CH2CH2O), 488 nm (1.99×104 dm3 mol-1 cm-1). 33.3 (NCH2CH2), 42.0 (NCH2), 67.9 (CH2O), 107.3 (C5,5), 121.2 (C4,4), 123.7 (C3,3), 136.6 (C3¾,5¾), 148.9 (C6,6), 156.0 Ruthenium(II ) ruthenium(III ) complex 13 (C2,2), 156.9 (C2¾,6¾), 167.1 (C4¾); IR (KBr), 3359, 3299, 3059, A solution of RuCl3·3H2O (80 mg, 306 mmol) and 12 (542 mg, 3014, 2947, 2865, 1598, 1583, 1576, 1470, 1448, 1410, 1358, 306 mmol) in MeOH (20 cm3) was refluxed for 6 h.After 1208, 1043, 803 cm-1. cooling to 25°C, the red precipitate was filtered, washed with cold MeOH (2 cm3), water (2×10 cm3), and dried in vacuo to Amino-ruthenium(II ) complex 11 yield crude product 13, as a dark-red solid (206 mg, 34% crude To a suspension of complex 9 (300 mg, 318 mmol) in MeOH yield); mp>152°C (decomp.); IR (KBr), 3425, 3071, 2980, (20 cm3) were added amine 10 (106 mg, 318 mmol) and 4- 2940, 1724, 1655, 1617, 1547, 1470, 1371, 1163, 847, 793 cm-1; ethylmorpholine (73 mg).The mixture was refluxed for 2 h UV–VIS, lmax=232 (e=7.25×104 ), 270 (7.53×104), 304 until it turned into a clear red solution.After cooling to 25°C, (7.49×104), 488 nm (2.06×104 dm3 mol-1 cm-1). This prod- saturated NH4PF6 in MeOH (10 cm3) was added, then the uct was not purified but carried on to the next reaction. methanol was removed in vacuo, the resulting red solid was dissolved in CHCl3 (4 cm3), which was then slowly added to Dendritic complex 14 Et2O (100 cm3) with stirring, to yield a red precipitate, which was filtered, and dried in vacuo to give complex 11, as a red To a suspension of complex 13 (429 mg, 216 mmol, 4.4 equiv.) solid (336 mg, 72%); mp>152 °C (decomp.); (Found: C, 49.92; in MeOH (30 cm3) were added tetrakisterpyridine core 5 H, 5.29; N, 7.28.C61H78F12N8O9P2Ru requires C, 50.24; H, (63.5 mg, 49 mmol) and 4-ethylmorpholine (45 mg) in MeOH– 5.39; N, 7.68%); 1H NMR (CD3CN), d 1.11–1.45 (m, 31H, CHCl3 (251, v/v, 5 cm3). The mixture was refluxed for 4 h NCH2CH2CH2, CH3 ) , 1.8–2.0 (m, 10H, CH2CH2O, until it turned into a clear red solution.After cooling to 25°C, OCH2CH2, CH2CH2CO2), 2.22 (m, 6H, CH2CO2), 2.45 (t, 2H, an excess of NH4PF6 was directly added to the solution to J 7.0 Hz, CH2CON), 3.00 (br s, 2H, H2NCH2), 4.52 (m, 4H, form a red precipitate, which was filtered, washed sequentially CH2O, OCH2), 6.67 (s, CONH), 7.16 (m, 4H, H5,5), 7.42 (m, with cold MeOH (2×5 cm3), water (2×15 cm3), Et2O 4H, H6,6), 7.88 (m, 4H, H4,4), 8.35–8.60 (m, 8H, H3,3, H3¾,5¾); (2×5 cm3), and dried in vacuo to yield 14, as a red solid 13C NMR (CD3CN), d 23.8 (NCH2CH2CH2), 25.0 (416 mg, 85%); mp 219–221 °C (Found: C, 47.66; H, 4.32; N, (CH2CH2CON), 28.4 (d, CH3, CH2CH2O), 29.7 (d, 7.95.C397H444F96N56O52P16Ru8 requires C, 47.87; H, 4.49; N, CH2CH2CO2 ), 32.7 (d, CH2CON, H2NCH2CH2), 7.88%); 1H NMR (CD3CN), d 1.30–3.90 (br m, 236H, CH2, 41.7(H2NCH2 ), 58.6 (NHC), 70.3 (OCH2), 71.1 (CH2O), 112.2 CH3), 4.53 (m, 40H, OCH2, CH2O), 6.47 (s, 4H, CONH), 7.15 (C5,5), 125.4 (C4,4), 128.5 (C3,3), 138.7 (C3¾,5¾), 153.5 (C6,6), (m, 32H, H5,5), 7.40 (m, 32H, H6,6), 7.86 (m, 32H, H4,4), 157.5 (C2,2), 159.4 (C2¾,6¾), 167.0 (d, C4¾), 172.9 (CONH), 173.7 8.35–8.60 (m, 64H, H3,3, H3¾,5¾); 13C NMR (CD3CN), d 23.1, (CO2 ); IR (KBr), 3417, 3295, 3086, 2980, 2940, 1719, 1614, 25.0, 25.9, 28.4 (CH3), 29.8, 29.9, 30.5, 30.6, 32.7, 32.8, 40.0 1470, 1394, 1370, 1213, 1162, 1040, 840, 788, 754 cm-1; (CONHCH2), 58.0 (CONHC), 68.0–70.0 (m, all CH2O, UV–VIS, lmax=244 (e=4.76×104 ), 270 (5.17×104), 304 OCH2), 81.3 (CO2C), 112.1 (d, C5,5), 125.5 (d, C4,4), 128.5 (6.08×104), 488 nm (1.81×104 dm3 mol-1 cm-1).(C3,3), 138.8 (C3¾,5¾), 153.5 (C6,6), 157.4 (C2,2), 159.4 (C2¾,6¾), 167.1 (d, C4¾), 172.4 (CONHC), 174.0 (CO2); IR (KBr), 3425, Complex 12 3118, 3079, 2979, 2941, 1724, 1671, 1617, 1547, 1470, 1425, 1217, 848, 786 cm-1; UV–VIS, lmax=244 (e=3.68×105 ), 270 To a solution of 4-[4¾-oxa-(2,2¾56¾,2-terpyridinyl)]butanoic (3.99×105), 304 (4.77×105), 488 nm (1.41×105 dm3 acid 6 (207 mg, 618 mmol) in dry DMF (15 cm3) were added mol-1 cm-1).DCC (128 mg, 618 mmol) and 1-HOBT (83.5 mg, 618 mmol) at 25°C. The mixture was stirred for 1 h, then amine 11 (901 mg, 618 mmol) was added. The whole mixture was stirred for 48 h, Results and Discussion after which the white precipitate was filtered.The red filtrate was concentrated in vacuo to aord a crude residue, which Synthesis of the tetrakisterpyridine core 5 was dissolved in CHCl3 (200 cm3), washed with saturated aqueous NaHCO3 (2×50 cm3), then brine (2×100 cm3), dried The synthesis of tetrakisterpyridine core 5 was initiated from the readily available tetracarboxylic acid 3, which has been (MgSO4), and concentrated in vacuo.The crude residue was column chromatographed eluting with 10% MeOH in CH2Cl2 demonstrated to be an ideal core for the construction of a four-directional dendritic materials.7 Acid 3, prepared10 in high to yield 12, as a red solid (465 mg, 42%); mp 90–94°C (Found: C, 53.95; H, 5.50; N, 9.47.C80H93F12N11O11P2Ru requires C, yield and purity from pentaerythritol and acrylonitrile, followed by hydrolysis, was reacted8 with BH3 in THF at 0°C 54.11; H, 5.28; N, 8.68%); 1H NMR, d 1.11–1.45 (m, 31H, NCH2CH2CH2, CH3 ) , 1.8–2.0 (m, 12H, OCH2CH2, to aord tetraol 4, which was then treated with at least 4 equivalents of 4¾-chloro-2,2¾56¾,2-terpyridine9 (4¾-Cl-tpy) in the CH2CH2O, OCH2CH2, CH2CH2CO2), 2.22 (m, 6H, CH2CO2), 2.40–2.46 (m, 4H, CH2CONH, CH2CONH), 3.10 (m, 2H, presence of powered KOH in anhydrous Me2SO at 60°C to give the desired tetrakisterpyridine core 5 in 74% yield after CONHCH2), 4.52 (m, 6H, OCH2, CH2O, OCH2), 6.56 (s, CONHC), 7.16–8.70 (m, tpy H); 13C NMR, d 23.1 purification, Scheme 1.The structure of core 5 was confirmed (1H NMR) by the definitive upfield shift (Dd=-0.52 ppm) for (NCH2CH2CH2 ), 25.0 (d, CH2CH2CONH, CH2CH2CONH), 28.0 (d, CH3, CH2CH2O), 29.8 (d, CH2CH2CO2), 31.7, 32.3, the singlet for the 3¾,5¾-terpy H upon the 4¾-terpy Cl to 4¾-terpy OR conversion. In 13C NMR, the peak shifts for the C5,5 from 32.7 (CH2CONH, H2NCH2CH2, CH2CONH), 39.2 1242 J.Mater. Chem., 1997, 7(7), 1237–1244d 121.1 to 107.3 and for C4¾ from d 146.5 to 167.1 further complex heteroaryl H region supports the presence of structurally dissimilar terpyridine environments. Whereas in its 13C support the transformation. NMR spectrum, the two pairs of dierent terpyridines aorded Synthesis of ruthenium(II ) complex connectors complex patterns with peaks for each carbon atom due to the small dierence caused by the two layers of ruthenium(II) 4-[4¾-Oxa-(2,2¾56¾,2-terpyridinyl)]butanoic acid 6, was pre- terpyridines centres connected by the slightly dierent organic pared by the reaction of 4¾-Cl-tpy with 4-hydroxybutanoic acid linkages.All signals (13C NMR) were, however, resolved to in the presence of solid KOH in anhydrous Me2SO at 60°C show each moiety of the dendritic complex, with the exception in 86% yield.The structure of 6 can be supported (NMR) by of the quaternary core carbon, which should have appeared at the shift of H3¾,5¾ at d8.46 to 7.92 denoting the formation of d 45.6; the absence of this signal is reasonable since it is the the 4¾-ethereal bond.By taking advantage of the peptide only unique atom in the dendritic assembly. coupling method11 (Scheme 2) using dicyclohexylcarbodiimide Hydrolytic or thermal deprotection, followed by subsequent (DCC) and 1-hydroxybenzotriazole (1-HOBT) in DMF, acid formation of a larger ‘dendritic’ surface can be accomplished 6 was reacted with ‘Behera’s amine’ 710 to aord terpyridine at either the appendage stage (8 or 12) or the four-directional amide 8 in 72% yield.The new peak (1H NMR) at d 6.03 dendrimer (14). The former oers solubility advantages as well denotes the formation of the amide bond. In 13C NMR, the as the ability to conveniently attach these metallo-modules to formation of the ethereal bond can be concluded based on the other macromolecular materials; applications of these metallo- significant shifts of C5,5 and C4¾; the successful amidation is macromolecules are in progress and will be reported elsewhere.supported by the shift of the signal assigned to newly introduced quaternary carbon moiety (CONHC) from d 52.8 to 57.6. The yellow–brown microcrystalline, paramagnetic Conclusion ruthenium(III ) complex 9 was prepared by refluxing 1 equival- The construction of this new type of double tiered metallodend- ent of 8 with RuCl3 3H2O in methanol to give 76% yield, rimer shows the importance of the stepwise construction by which was used without further purification.means of controlled metal complexation. This modular Preferential O- vs. N-arylation was realized when 5-amino- approach also provides a much more versatile methodology pentan-1-ol was reacted with 4¾-Cl-tpy in the presence of for the synthesis of specifically assembled metallodendrimers powered KOH in dry Me2SO to aord the free 5-aminopentyl and related polymers by using a combination of divergent and 4¾-(2,2¾56¾,2-terpyridinyl) ether 10 in 71% conversion, convergent approaches.Scheme 3.The structure of 10 was readily confirmed by the lack of change for the signals of H2NMCH2 in both 1H and This work was supported, in part, by the National Science 13C NMR spectra. The significant chemical shifts (1H NMR) Foundation (DMR-96–22609) and the Army Research Oce for H3¾,5¾ and C5,5, as well as for C4¾ (13C NMR) confirmed (DAAH04–93-G-0448). the free amino group and the preferential formation of the 4¾- ethereal bond.The aminoterpyridine 10 was then reacted with 1 equivalent of the ruthenium(III ) complex 9 in boiling meth- References anol and N-ethylmorpholine, as the reducing agent, followed by addition of an excess of NH4PF6, to aord the amino 1 For recent reviews see: (a) G. R. Newkome, C. N. Moorefield and F. Voegtle, Dendritic Molecules: Concepts, Syntheses, Perspectives, complex 11, as a red hexafluorophosphate salt in 72% yield.VCH,Weinheim, 1996;(b) N. Ardoinand D. Astruc,Bull. Soc. Chim. Confirmation of the structure of this ruthenium(II) complex Fr., 1996, 132, 875; (c) B. I. Voit, Acta Polym., 1995, 46, 87; (d) was demonstrated by the upfield shift (Dd=-1.23 ppm) for J. Issberner, R. Moors and F. Voegtle, Angew.Chem., Int. Ed. Engl., H6,6 in 1H NMR, and all downfield shifts of C5,5 from d 1994, 106, 2507; (e) J. M. J. Fre� chet, C. J. Hawker and K. L.Wooley, 107.3 to 112.2, C4,4 from d 121.2 to 125.4, C3,3 from d 123.7 J.Macromol. Sci. Part A, 1994, 31, 1627; (f ) J. M. J. Fre� chet, Science, to 128.5, C3¾,5¾ from d 136.6 to 138.7, C6,6 from d 148.9 to 1994, 263, 1710; (g) D.A. Tomalia, A. M. Naylor and W. A. Goddard, III, Angew Chem., Int. Ed. Engl., 1990, 29, 138. 153.5, C2,2 from d 156.0 to 157.5, C2¾,6¾ from d 156.9 to 159.4; 2 M. F. Ottaviana, S. Bossmann, N. J. Turro and D. A. Tomalia, notably the signal for C4¾ remained nearly constant. J. Am. Chem. Soc., 1994, 116, 661. Reaction of acid 6 with amine 11 was accomplished by using 3 For metallo-related dendrimer reviews: Advances in Dendritic the DCC coupling method, as described above, to give (42%) Macromolecules, ed.G. R. Newkome, JAI Press, Greenwich, CT, the complex 12, as a red solid. Any unreacted acid 6, which 1996, vol. 3, ch 3: S. Serroni, S. Campagna, G. Denti, A. Juris, contains the uncomplexed terpyridine moiety, was eliminated M. Venturi and V. Balzani, pp. 61–113; ch. 4: M. R. Bryce and W. Devonport, pp. 115–149; ch. 5: I. Cuadrado, M. More�n, by column chromatography so that no unexpected metal J. Losada, C. M. Casado, C. Pascual, B. Alonso and F. Lobete, complexation sites would be carried to the subsequent reaction. pp. 151–195. Other references not included in ref. 1: (a) R. L. C. Lau, An equimolar solution of ligand 12 with RuCl3·3H2O in T-W.D. Chan, I. Y.-K. Chan and H.-F. Chow, Eur.Mass Spectrom., methanol was refluxed to give the red paramagnetic complex 1995, 1, 371; (b) M.Haga, M. M. Ali and R. Arakawa, Angew. Chem., 13, which was filtered from the miin 34% crude yield, Int. Ed. Engl., 1996, 35, 76; (c)W. T. S. Huck, F. C. J. M. van Veggel Scheme 4. and D. N. Reinhoudt, Angew. Chem., Int. Ed.Engl., 1996, 35, 121; (d) U. Stebani, G. Lattermann, M. Wittenberg and J. H. Wendor, Angew. Chem., Int. Ed. 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