James McCusker
Research
Synthesis and Spectroscopy of Transition Metal Complexes
(Research Description PDF)
The McCusker Group is interested in the physical and photophysical properties of transition metal complexes. Our approach relies on a confluence of synthetic chemistry, a host of physical techniques ranging from magnetism to femtosecond time-resolved spectroscopy, and high-level theory. The simultaneous examination of chemical problems on all three of these fronts places us in a unique position to explore the physical chemistry of inorganic compounds.
Ultrafast Spectroscopy of Transition Metal Complexes. Our research efforts in this area concern the short time scale photo-induced dynamics of transition metal complexes. By “short time scale”, we refer to processes occurring between the time a photon is absorbed by a molecule and the point at which that molecule is fully relaxed in its lowest-lying excited state. Some of the questions we are addressing with this research include the following: 1) what is the general time scale for excited-state evolution in transition metal complexes? 2) what is the mechanism of this process? 3) how do the geometric and electronic structures of the compounds, the surrounding medium, and other factors couple to and/or influence this process? and 4) to what extent can we use this information to control excited-state dynamics? Certain of these questions are very fundamental in nature, whereas others are geared toward work on solar energy conversion. What distinguishes the group, we believe, is our ability to carry out both the synthesis and spectroscopic characterization of a wide range of inorganic molecules. This enables us to systematically examine chemical perturbations to excited-state electronic and geometric structure, and in so doing develop a comprehensive picture of how transition metal chromophores absorb and dissipate energy.
Spin and Spin Polarization Effects on Excitedstate Dynamics. Electron spin is a fundamental property of Nature. Although many of the more common
physical observables linked to spin are well documented (e.g., magnetism), the degree
to which spin and spin polarization influences the chemistry of molecular systems
is not as clear. We are pursuing the design and development of chemical systems that
will allow us to determine whether there exists a cause-and-effect relationship between
the physical and photophysical properties of molecules and their innate spin properties,
and if so, to what extent can we exploit this connection in order to manipulate the
chemistry of molecular systems. Much of this work centers on the study of so-called
donor-acceptor assemblies wherein energy and electron transfer processes are being
examined in systems containing spin-coupled paramagnetic fragments. Through careful
synthetic manipulation of these compounds, correlations between the observed excitedstate
reactivity and the involvement of spin-polarized electronic states of the donor
and/or acceptor can be realized. Coupled to this experimental work are theoretical
studies that exploit recent advances in density functional theory. We believe that
these combined efforts will forge an important link between magnetisn and electron/energy
transfer processes, thereby allowing us to establish a new paradigm in the emerging
field of molecular spintronics.