Structural Modification on Copper(I)-pyridylpyrimidine Complexes for Modulation of Rotational Dynamics, Redox Properties, and Phototriggered Isomerization

The redox properties of copper pyridylpyrimidine complexes, which undergo linkage isomerism based on pyrimidine ring rotation, were compared under different coordination environments. A newly synthesized compound, [Cu­(Mepypm)­(LMes)]­BF4 (1·BF4, Mepypm = 4-methyl-2-(2′-pyridyl)­pyrimidine, LMes = 2,9-dimesityl-1,10-phenanthroline) was compared with previously reported complexes of [Cu­(MepmMepy)­(LMes)]­BF4 (2·BF4, MepmMepy = 4-methyl-2-(6′-methyl-2′-pyridyl)­pyrimidine), Cu­(Mepypm)­(DPEphos)]­BF4 (3·BF4, DPEphos = bis­[2-(diphenylphosphino)­phenyl]­ether), [Cu­(Mepypm)­(LAnth)]­BF4 (4·BF4, LAnth = 2,9-bis­(9-anthryl)-1,10-phenanthroline), and [Cu­(Mepypm)­(LMacro)]­BF4 (5·BF4). Isomer ratios, isomerization dynamics, redox properties, and photoelectron conversion functions varied with the coordination structure. Methyl substituents on the 6-position of the pyridine moiety increased steric repulsion and contributed to quicker rotation, enhanced photoluminescence, and increased photodriven rotational isomerization.