Gloveboxes & Fume Hoods

We are an organometallic research group, with an expertise in synthetic inorganic chemistry. We are specifically interested in the chemistry of the f-block elements, which comprises the lanthanides and actinides. Through reactivity and structure/property relationship studies, we can carefully design and synthesize complexes to address problems in areas such as quantum information science, energy, and catalysis. We use traditional Schlenk and glovebox techniques to handle highly air- and moisture sensitive complexes. Pictured here are a few of our gloveboxes and fume hoods!

Electron Paramagnetic Resonance

Continuous wave (CW) EPR. The characterization and understanding of open-shell systems is an important tool for not only the development of high-performing molecular quantum materials, but also provides a platform to gain a deeper insight into the electronic states innate to metal centers. In the presence of a magnetic field, unpaired electrons split into multiple states. Electron Paramagnetic Resonance (EPR) spectroscopy interrogates these energy differences through excitation of the electron with static microwave irradiation whilst sweeping the magnetic field. Once the microwave radiation resonates with the energy difference between the spin up and down state, a signal is observed. The so-called CW-EPR spectra can be collected at multiple different frequencies depending on the spin system: S-band (2-4 GHz), X-band (8-10 GHz), Q-band (35 GHz), and W-band (90 GHz). X-band EPR spectroscopy is typically employed to characterize organic-based open-shell systems. The coupling of the electronic spins to nuclear spins results in fine structure which translates into intricate EPR spectra. Judicious simulation of the spectra by alteration of hyperfine couplings provides insight into the spin system and can help discern many important factors such as spin density. See our recent work employing cw-ERP!

Pulsed EPR techniques. Pulsed EPR spectroscopic methods shed light onto the nature of electronic spin and the origin of relaxation times. The standard CW-EPR instrument can be slightly modified to generate microwave pulses that are used to perturb the orientation of the magnetization vector of electronic spins present in the query sample. Various pulse sequences allow investigations of different relaxation times most notably the spin-lattice relaxation time (T₁) and the dephasing time (T₂). In addition, interactions existing between electronic spin and neighboring spins can be also probed. The Demir group utilizes pulsed EPR techniques such as ESEEM (Electron Spin Echo Envelope Modulation), HYSCORE (Hyperfine Sublevel Correlation), Inversion Recovery and CPMG (Carr-Purcell-Meiboom-Gill) to study both the electronic structure of molecules comprising unpaired electrons and the relaxation times innate to compounds as potential quantum bits. See how we used pulsed EPR in our research!

Nuclear Magnetic Resonance

In addition to routine ¹H and ¹³C NMR techniques, the Demir Group focuses on the characterization of new organometallic and coordination yttrium complexes using ⁸⁹Y NMR spectroscopy. The 100% natural abundance and I = 1/2 of the ⁸⁹Y isotope, enables investigations towards the influence of the ligand field on the metal nucleus. The ⁸⁹Y nucleus is sensitive to subtle changes in the coordination sphere giving rise to a spectral window of ~1300 ppm. Thus, the Demir Group seeks to elucidate the contributions of coordination number, ligand scaffold, solvent coordination, and nuclearity to the ⁸⁹Y chemical shift. Furthermore, the trivalent metal ion exhibits similarities in reactivity and ionic radii with the mid-sized lanthanides and thus, can serve as a diamagnetic surrogate for paramagnetic lanthanide analogs. The latter engender significant line broadening, paramagnetic shifts, and rapid relaxation of resonance signals. Check our recent paper utilizing ⁸⁹Y NMR!

Single Crystal X-ray Diffraction

Complete characterization of the newly synthesized organometallic complexes isolated by our group necessitates structural determination by single-crystal X-ray crystallography. This technique is used to determine the precise spatial arrangement of atoms within a crystalline material through interaction of X-rays with the electron density of the molecule. Thorough investigation of the crystal structure allows for the realization of structure-property relationships which can illuminate the deliberate design and isolation of next-generation organometallic-based quantum materials. The X-ray facility at Michigan State University has recently been outfitted with Rigaku Synergy S single-crystal X-ray diffractometers which allow for rapid data collection, and have the capability to collect full data sets at several different temperatures. The strength of this technique is showcased in one of our recent publications where the structural dependence on temperature is determined for a heteroleptic rare-earth tris(metallocene).

Density Functional Theory

The Demir group explores rare earth (RE) and uranium complexes featuring unprecedented bonding motifs of organic ligands in differing oxidation states and heavy p-block elements. Quantum chemical calculations via Density Functional Theory (DFT) are performed to gain insights in the intricate electronic structure of these compounds and to uncover the nature of RE and U ligand bonding interactions. The nature of chemical bonds is investigated through natural bond orbital (NBO) analysis, which provides a detailed description of atomic orbitals participating in a given atomic array. For radical-containing complexes, unrestricted DFT calculations allow us to probe the spin density delocalization which is associated with magnetic coupling.  DFT is also employed for the calculation of spectroscopic properties such as infrared (IR), UV/vis and electron paramagnetic resonance (EPR) spectra which aids the interpretation of the frequently convoluted experimental spectra. In addition, nuclear independent chemical shift (NICS) calculations are conducted to study the aromaticity of coordinated pi-electron delocalized ligands. The Demir group has access to the state-of-the-art program suites Gaussian 16 and Orca 5.0 which are provided by the Institute for Cyber-Enabled Research (https://icer.msu.edu/) at MSU.