Syntheses, structure, and molecular cubic hyperpolarizabilities of systematically varied ethynylgold(I) complexes

The reactions of Q[Au(acac)(2)] (Q = N(PPh3)(2) (PPN; a), NPr4 (b); acac = acetylacetonato) with terminal alkynes of the type HC=CC6H4R-4 in a 1:2 molar ratio affords the complexes Q[Au(C=CC6H4R-4)(2)] (R = NO2 (1), C6H4NO2-4 (2), (E)-CH=CHC6H4NO2-4 (3)). The same alkynes react with [AuCl(CNBut)] in NEt3 to give the complexes [Au(C=CC6H4R-4)(CNBut)] (R = NO2 (4), C6H4NO2-4 (5), (E)-CH=CHC6H4NO2-4 (6)). When NHEt2 is used instead of NEt3, attack of the secondary amine at the isonitrile ligand takes place and alkynyl carbene complexes of the type [Au(C=CC6H4R-4){C(NHBut)(NEt2)}] (R = NO2 (7), C6H4NO2-4 (8), (E)-CH=CHC6H4NO2-4 (9)) are obtained. The crystal structures of 1a, 4, 7, and 9 have been determined. The cubic hyperpolarizabilities of 1a,b, 4-6, 8, 9, and the related complexes [Au(C=CC6H4R-4)(PPh3)] (R = H (10), NO2 (11), 4-C6H4NO2 (12), (E)-CH=CHC6H4NO2-4 (13), C=CC6H4NO2-4 (14), (Z)-CH=CHC6H4NO2-4 (15), (E)-N=CHC6H4NO2-4 (16)) have been determined by Z-scans at 800 nm. An increase in gamma(real) is observed on replacing the coligand (BuNC)-N-t by PPh3 (proceeding from 5 to 12 and from 6 to 13), introduction of the NO2 group (proceeding from 10 to 11), extending the arylalkynyl pi-bridge (proceeding from 11 to 12-15), and replacing (Z)-CH=CH by the (E)-CH=CH linking unit (proceeding from 15 to 13).