Liquid-Crystalline Mono- and Dinuclear (Perhalophenyl)gold(I) Isocyanide Complexes

Rodlike gold(I) and gold(III) complexes [AuR(CN(C(6)H(4))(m)()OC(n)()H(2)(n)()(+1)-p)] (m = 1, n = 10, R = C(6)F(5); m = 2, n = 4, 6, 8, 10, 12, R = C(6)F(5), C(6)F(4)Br-o, C(6)F(4)Br-p), [(-4,4'-C(6)F(4)C(6)F(4)){AuCN(C(6)H(4))(m)()OC(n)()H(2)(n)()(+1)}(2)] (m = 1, 2; n = 4, 6, 8, 10, 12), [AuRI(2)(CNC(6)H(4)C(6)H(4)OC(n)()H(2)(n)()(+1)-p)] (R = C(6)F(5), n = 8; R = C(6)F(4)Br-o, n = 10), and [(-4,4'-C(6)F(4)C(6)F(4)){AuX(2)CN(C(6)H(4))(m)()OC(n)()H(2)(n)()(+1)}(2)] (m = 1, 2; n = 4, 6, 8, 10, 12) have been prepared and their liquid crystal behavior has been studied. The gold(III) compounds are not mesomorphic, but all the perhalo-gold(I) derivatives described are liquid crystals except the phenyl isocyanide gold(I) derivative [Au(C(6)F(5))(CNC(6)H(4)OC(10)H(21)-p)]. The mononuclear derivatives show only a nematic (N) phase when the isocyanides have a short tail (n = 4), N and smectic A phases (S(A)) when the isocyanides have an intermediate tail (n = 6, 8), and only S(A) phases for longer chains. Their thermal stability is high, even in the isotropic state. The variation in transition temperatures is as follows: C(6)F(4)Br-p >/= C(6)F(5) > C(6)F(4)Br-o when n </= 6 and C(6)F(4)Br-p > C(6)F(4)Br-o > C(6)F(5) for n >/= 8. This behavior is understood on the basis of electronic and steric factors. The dinuclear compounds [(-4,4'-C(6)F(4)C(6)F(4)){AuCN(C(6)H(4))(m)()OC(n)()H(2)(n)()(+1)}(2)] display only N mesophases and all the biphenylisocyanide derivatives and phenyl isocyanide compounds with n </= 6 undergo some decomposition upon reaching the clearing point to the isotropic state.