Vinylogue Mono- and Bimetallic Cationic Sesquifulvalene and Monohydro Sesquifulvalene Complexes for Second Harmonic Generation

摘要

The donor-acceptor complexes with a vinylogue monohydro sesquifulvalene and sesquifulvalene backbone of the type [(η~5-C_5H_5)Ru{μ-(η~5-C_5H_4)C_2H_2(η~6-C_7H_7)}ML](PF_6)_n [n = 0: ML = none (1), Cr(CO)_3 (2); n = 1: ML = Ru(η~5-C_5H_5) (3a), Ru(η~5-C_5Me_5) (3b)] and [(η~5-C_5H_5)Ru{μ-(η~5-C_5H_4)C_2h_2(η~7C_7H_6)}ML](PF_6)_n [n = 1: ML = none (4), Cr(CO)_3 (5); n = 2: ML = Ru(η~5-C_5H_5) (6a), Ru(η~5-C_5Me_5) (6b)], respectively, have been synthesised, and spectroscopically and structurally characterised. A charge-shift correlation was carried out by means of ~1H NMR spectroscopic studies and an increased ground-state donor-acceptor interaction in the order 5 < 6b < 4 < 6a was found. The corresponding donor-acceptor interaction in 3a and 3b varies by an insignificant amount. Hyper-Rayleigh scattering (HRS) was applied to determine the first hyperpolarisability β of the mono- and dicationic complexes 3a-6b. The β values obtained for the cationic sesquifulvalene complexes 4-6b are among the largest ever measured for ruthenocenyl containing complexes due to a strong resonance enhancement: the sesquifulvalene complexes 4-6a, 5b show first hyperpolarisabilities which range between 360 and 700 * 10~(-3) esu, whereas β for the monohydrosesquifulvalene complexes are considerably lower (75 and 162 * 10~(-30) esu). For the latter complexes the first hyperpolarisability doubles on going from Ru(η~5-C_5Me_5) (3b) to Ru(η~5-C_5H_5) (3a) in the acceptor unit.