Author ORCID Identifier

https://orcid.org/0009-0005-8919-2292

Semester

Fall

Date of Graduation

2025

Document Type

Dissertation (Campus Access)

Degree Type

PhD

College

Eberly College of Arts and Sciences

Department

Chemistry

Committee Chair

Brian S. Dolinar

Committee Member

Brian V. Popp

Committee Member

Fabien Goulay

Committee Member

Stephen J. Valentine

Committee Member

Mikel Holcomb

Abstract

Low-coordinate transition metal compounds have historically been challenging to synthesize due to the coordinatively unsaturated metal center’s tendency to stabilize through higher coordination numbers or oxidation states. Nevertheless, owing to their versatile applicability in catalytic activity, small molecule activation and molecular magnetism, low-coordinate TM systems have garnered increasing attention from synthetic chemists. This thesis presents the development of a super-bulky carbazole based ligand primarily designed to access low-coordinate TM compounds. Detailed structural, electrochemical and photophysical characterization of the ligand were performed using X-ray crystallography, cyclic voltammetry and electronic absorption and emission experiments. Additionally theoretical methods were employed to gain deeper insight into the electronic structure and optical transitions of the system. The protonated ligand exhibits a remarkable quantum yield of 83% determined by the comparative method and an excited state lifetime of 7 ns. The corresponding potassium carbazolide displays bi-exponential decay components suggesting presence of thermally activated delayed fluorescence. A series of two-coordinate first-row transition metal compounds, M((tBu)2carb(Ph2CH)2)2 (M = Mn, Fe, Co) supported by the carbazole ligand were synthesized and thoroughly characterized utilizing both experimental and theoretical methods. Magnetic properties were probed by SQUID magnetometry, while DFT and CASSCF/NEVPT2 methods were utilized to elucidate the electronic structure of the compounds and their unique magnetic properties. The cobalt compound, Co((tBu)2carb(Ph2CH)2)2 displays slow magnetic relaxation under an applied magnetic field with an effective energy barrier of 30.2 K and a large negative D of -169 cm-1. NEVPT2 calculations reveal a non-Aufbau ground state electronic configuration for the cobalt compound, accounting for the experimentally observed magnetic anisotropy. In efforts to suppress quantum tunneling of magnetization, a trinuclear Fe3 compound was synthesized. X-ray crystallography confirms the molecular structure with a linear Fe3 core. CASSCF calculations predict negative D values of -19 cm-1 and -9 cm-1 for the terminal and central iron atoms respectively. Broken symmetry DFT calculations suggest dominant ferromagnetic coupling interactions within the Fe3 core. Together these calculated results point toward promising magnetic behavior and highlight the need for further experimental investigations.

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