Tuning of the Electronic and Optical Properties of Manganese(I) Sesquifulvalene Complexes

Template syntheses of sesquifulvalenes (2,4,6-cycloheptatrien-1-ylidene)cyclopentadiene ( 1 ) and [(2,4,6-cycloheptatrien-1-ylidene)ethenylidene]cyclopentadiene ( 2 ) lead to air-stable complexes [( 1 )Mn(CO) 2 L]BF 4 ( 4 ) and [( 2 )Mn(CO) 2 L]BF 4 ( 8 ) ( a, L = CO; b, L = P(OMe) 3; c, L = PPh 3 ). The different σ-donor/π-acceptor abilities of the ligands L allow a tuning of the electronic and optical properties of complexes 4 and 8, which are particularly studied by UV/vis spectroscopy. The first molecular hyperpolarizabilities β of complexes 4 and 8 have been determined in dichloromethane and acetonitrile solutions by hyper Raleigh scattering. The X-ray crystal structures of 4b, 8b, and of the alkenylcyclopentadienyl complex [4,5η-(2,4,6-cycloheptatrien-1-yl)-η 5 -cyclopentadienyl]dicarbonylmanganese(I) ( 5 ) are reported.