Optosensing properties of fac-Re(CO)3(dpknph)Cl (dpknph=di-2-pyridyl ketone p-nitrophenyl hydrazone) toward chemotactic N-formylamino acids

Optical measurements on fac-Re(CO)3(dpknph)Cl in polar non-aqueous solvents in the presence and absence of NaBH4/KPF6 revealed reversible interconversion between the high (β-) and low (α-) energy electronic states of fac-Re(CO)3(dpknph)Cl. The reversibility of these interactions and the disturbance of the equilibrium distribution of the low (α-) and high (β-) energy electronic state upon addition of NaBH4/KPF6 mark improvement in the optosensing properties of fac-Re(CO)3(dpknph)Cl. The optical behavior of fac-Re(CO)3(dpknph)Cl in the presence and absence of the l-methionine and chemotactic N-formylamino acids: N-formyl-l-methionine (NFM), N-formyl-l-glycine (NFG) and N-formyl-l-phenylalanine (NFP) shows the α- and β-electronic states of fac-Re(CO)3(dpknph)Cl to be insensitive to l-methinonine and highly sensitive to N-formylamino acids. N-formylamino acids in concentrations <1.0×10−5 M can be determined using the optical sensor fac-Re(CO)3(dpknph)Cl in non-aqueous polar solvents. The optosensing power of fac-Re(CO)3(dpknph)Cl towards N-formylamino acids depends on the concentration and polarity of the side chain of the amino acids and increases in the following order: NFM>NFG>NFP.