Rhenium(I) coordinated lumazine and pterin derivatives: structure and spectroelectrochemistry of reversibly reducible (6-ATML)Re(CO) 3Cl (6-ATML=6-acetyl-1,3,7-trimethyllumazine)

Abstract

A number of complexes between substituted lumazines (2,4-dioxo-(1 H,3 H)pteridines) or pterins (2-amino-4-oxo-(3 H)pteridines) and Re(CO) 3Cl have been synthesized and characterized electrochemically and spectroscopically. The structure of the (6-ATML)Re(CO) 3Cl derivative (6-ATML=6-acetyl-1,3,7-trimethyllumazine) could be determined in [ fac-(6-ATML)Re(CO) 3Cl]·3C 6H 6. The rhenium(I) center coordinates in a rather symmetrical fashion through the O4–N5 α-carbonylimino chelate site of 6-ATML; the potentially available acetyl function is not involved in the metal coordination. The acetyl acceptor substituent facilitates the reversible one-electron reduction of this compound to a persistent anion radical complex [(6-ATML)Re(CO) 3Cl] −, which is accompanied by variable low-frequency shifts of the six carbonyl stretching bands and by the appearance of a broad EPR signal.