Absorbance and emission studies in solution and the solid state and band gap determination of Pri3Ge(GePh2)4GePri3

The hexagermane Pri3Ge(GePh2)4GePr i3 (1) can adopt four different conformations by rotations about its germanium –germanium single bonds that differ in energy across an energy range of 31.63 kJ/mol, with the trans-coplanar arrangement having the lowest energy. Conformational changes can occur among these four structures resulting in the observation of thermochromic absorbance spectra both in solution and in the solid state. Bathochromic shifts of 5 nm and 15 nm were observed in solution and in the solid state with increasing temperature. Compound 1 is also luminescent both in solution and in the solid state. The solution emission spectra are solvent dependent and the solid state emission maxima were shown to be temperature dependent. When 1 is excited at 300 nm in the solid state at 80 K its emission spectrum contains a broad emission peak in the visible region and this emission can be observed with the naked eye. The indirect band gap of 1 was determined to be 3.25 eV, which is consistent with investigations on other related oligogermane systems.