Hydrogen Bonding and Environment Effects on N-Retinylidene N-Butyliminium Salts

Protonated (or deuterated) all-trans, N-retyniliden, n-butylimine (NRB) with three different counter anions, (CF3)2CHO−, Cl− and BF4 − in various organic environments were used as model systems for protein-bound retinal in halorhodopsin. We have employed UV-Visible absorption and vibrational spectroscopies to study environmental and hydrogen bonding effects on the ground and excited state properties of NRB in order to gain more insight into the molecular interactions in the retinal binding pocket of the biological system.