Synthesis and Nonlinear Optical Properties of Carbonylrhenium Bromide Complexes with Conjugated Pyridines

Carbonylrhenium bromide complexes fac-Br(OC)3ReL2 (3a,b, 4a,b) and cis-Br(OC)4ReL (5a,b) with conjugated pyridines L = Fc–CH=CH–p-C5H4N (1a), Fc–CH=CHC(CH3)=CHCH=CHCH=C(CH3)CH=CH–p-C5H4N (1b), 1,1′-Fc(–CH=CH–p-C5H4N)2 (1c), p-Me2N–C6H4–CH=CHCH=CH–p-C5H4N (2a), and p-Me2N–C6H4–CH=CHC(CH3)=CHCH=CHCH=C(CH3)–CH=CH–p-C5H4N (2b) have been synthesized. The structures of 4a and 5a have been determined by X-ray diffraction analysis. Compound 4a exhibits a remarkable quadratic hyperpolarizability.