Photophysical and nonlinear optical properties of μ-oxo-bridged indium and gallium phthalocyanines

The photophysical and nonlinear optical properties of a μ-oxo-bridged phthalocyanine heterodimer, i.e., [tBu4PcGa-O-InPctBu4] (5), where gallium is located in one macrocycle and indium is on the other macrocycle and the two metal atoms are connected through oxygen, have been described. Its photophysical properties are compared with the dimers: [tBu4PcGa]2O (3) and [tBu4PcIn]2O (4). The very small shifts of Q- and B-bands for all μ-oxo Pc dimers 3–5 relative to the starting materials tBu4PcGaCl (1) and tBu4PcInCl (2) is indicative of a very weak interaction between two phthalocyanine rings in the ground state. The deactivation processes of the excited singlet state of 5 occur independently for tBu4PcGa-O-moiety and tBu4PcIn-O-moiety. Dimerization in the manner of 5 has no advantages over 3 and 4 from the point of view of optical limiting as it does not increase the ratio of the excited to ground state absorption cross-sections nor does it reduce the saturation energy density.