“…Single-crystal X-ray analysis shows "equatorial", "axial", and intermediate structures. 49,50,57,62,64 The energy difference between two conformations, estimated through B3LYP/6-31G** or HF/6-31G** calculations, does not exceed 3 kJ/mol, which may imply that in solution at roomtemperature one could find a statistical mixture of both conformers. Therefore, we study both "equatorial" and "axial" structures of compounds 5-8 with strong TPA absorbancies to consider the impact of the conformational geometry on the optical properties of the chromophores.…”