Synthesis, crystal structure and optical properties of Me(OH)(HCOO)2 (Me = Al, Ga)

The formation conditions, crystal structure and luminescence properties of aluminum and gallium hydroxide diformates, Me(OH)(HCOO)(2), have been established. Both compounds crystallize in a monoclinic lattice ( space group C2, #5 and Z = 8) with parameters: a = 8.8629(2) angstrom, b = 9.9890(2) angstrom, c = 10.2411(1) angstrom, beta = 106.223(1)degrees, and V = 870.56(3) angstrom(3) (Al) and a = 8.8746(1) angstrom, b = 10.3291(1) angstrom, c = 10.27870.9) angstrom, beta = 105.7565(6)degrees, and V = 906.81(2) angstrom(3) (Ga). The emission spectra of Me(OH)(HCOO)(2) under UV excitation with wavelength lambda = 285 nm exhibit maxima in the range of 440-470 nm. The emission accompanied by light-blue luminescence is greatly enhanced when going from the aluminum to the gallium compound. The origin of intrinsic emission centers responsible for the luminescence properties of Me(OH)(HCOO)(2) is suggested and the higher emission of the gallium hydroxide diformate is substantiated by means of density-functional theory calculations.