Effect of Intermolecular Interactions on Metal‐to‐Metal Charge Transfer: A Combined Experimental and Theoretical Investigation

Understanding the effects of intermolecular interactions on metal‐to‐metal charge transfer (MMCT) is crucial to develop molecular devices by grafting MMCT‐based molecular arrays. Herein, we report a series of solvent‐free {Fe 2 Co 2 } compounds sharing the same cationic tetranuclear {[Fe(PzTp)(CN) 3 ] 2 [Co(dpq) 2 ] 2 } 2+ (PzTp − =tetrakis(pyrazolyl)borate, dpq=dipyrido[3,2‐ d :2′,3′‐ f ]quinoxaline) square units but having anions with different size, including BF 4 − , PF 6 − , OTf − , and [Fe(PzTp)(CN) 3 ] − . Intermolecular π⋅⋅⋅π interactions between dpq ligands, which coordinate to cobalt ions in the {[Fe(PzTp)(CN) 3 ] 2 [Co(dpq) 2 ] 2 } 2+ units, can be modulated by introducing different counterions, regulating the distortion of the CoN 6 octahedron and ligand field around the cobalt ions. This change results in different MMCT behavior. Computational analyzes reveal the substantial role of the intermolecular interactions tuned by the presence of different counteranions on the MMCT behavior.