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-cyclobeptatrien-1-ylidene)etheneylidene]cyclopentadiene (2) lead to air-stable complexes [(1)Mn(CO)(2)L]BF4 (4) and [(2)Mn(CO)(2)L]BF4 (8) (a, L = CO; b, L = P(OMe)(3); c, L = PPh(3)). The different sigma-donor/pi-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 beta 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 [4,5 eta-(2,4,6-cyclohepeatrien-1-gamma l)-eta(5)-cyclopentadienyl]dicarbonylmanganese(I) (5) are reported.