Asymmetric Ligand Field Effects in Electron-Rich Heterometallic Extended Metal Atom Chain Compounds.

Area of Science:

• Inorganic Chemistry
• Materials Science
• Coordination Chemistry

Background:

• Ligand electron donation typically influences metal atoms symmetrically in heterometallic systems.
• Electronegativity often dictates preferential metal atom interaction with electron-donating ligands.
• Previous studies on heterometallic extended metal atom chain (HEMAC) complexes provide a baseline for comparison.

Purpose of the Study:

• To synthesize and characterize novel HEMAC complexes with modified ligands.
• To investigate the electronic effects of electron-donating substituents on metal centers within HEMACs.
• To determine if electron donation from ligands impacts metal atoms symmetrically or asymmetrically.

Main Methods:

• Synthesis of Mo2M'(dedpa)4Cl2 complexes (M' = Cr, Mn, Fe, Co, Ni).
• Characterization using crystallography, magnetometry, cyclic voltammetry, EPR, Mössbauer, and electronic absorption spectroscopy.
• Computational analysis via Density Functional Theory (DFT) calculations.

Main Results:

• The synthesized heterometallic compounds (HEMACs) are more electron-rich and easier to oxidize.
• Ethyl substituents on the 4,4'-diethyl-2,2'-dipyridylamine (dedpa) ligand influenced metal centers asymmetrically.
• The ligand field was stronger at the Mo2 site but weaker at the M' center compared to analogous dpa complexes.
• New electronic transitions, potentially a triplet δ-δ* state, were observed.

Conclusions:

• The electron-donating ethyl groups on the dedpa ligand lead to asymmetric electronic influence on the metal atoms in HEMACs.
• This asymmetry challenges the conventional understanding of ligand effects in heterometallic systems.
• The observed changes in ligand field strength and new electronic transitions offer insights into tuning HEMAC properties.