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The first complexes containing a 2,3,4,5-tetraiodopyrrolyl anion as a ligand were isolated. The ligands' tendency to foster intermolecular σ-hole interactions was probed and compared to rare earth metal complexes bearing a 2,5-dimethylpyrrolyl anion. 

Abstract A number of technologies would benefit from developing inorganic compounds and materials with specific electronic and magnetic exchange properties. Unfortunately, designing compounds with these properties is difficult because metal⋅⋅⋅metal coupling schemes are hard to predict and control. Fully characterizing communication between metals in existing compounds that exhibit interesting properties could provide valuable insight and advance those predictive capabilities. One such class of molecules are the series of Lindqvist iron‐functionalized and hexavanadium polyoxovanadate‐alkoxide clusters, which we characterized here using V K‐edge X‐ray absorption spectroscopy. Substantial changes in the pre‐edge peak intensities were observed that tracked with the V 3d‐electron count. The data also suggested substantial delocalization between the vanadium cations. Meanwhile, the Fe^IIIcations were electronically isolated from the polyoxovanadate core. 

Abstract Large separation of magnetic levels and slow relaxation in metal complexes are desirable properties of single‐molecule magnets (SMMs). Spin‐phonon coupling (interactions of magnetic levels with phonons) is ubiquitous, leading to magnetic relaxation and loss of memory in SMMs and quantum coherence in qubits. Direct observation of magnetic transitions and spin‐phonon coupling in molecules is challenging. We have found that far‐IR magnetic spectra (FIRMS) of Co(PPh₃)₂X₂(Co‐X; X=Cl, Br, I) reveal rarely observed spin‐phonon coupling as avoided crossings between magnetic andu‐symmetry phonon transitions. Inelastic neutron scattering (INS) gives phonon spectra. Calculations using VASP and phonopy programs gave phonon symmetries and movies. Magnetic transitions among zero‐field split (ZFS) levels of theS=3/2 electronic ground state were probed by INS, high‐frequency and ‐field EPR (HFEPR), FIRMS, and frequency‐domain FT terahertz EPR (FD‐FT THz‐EPR), giving magnetic excitation spectra and determining ZFS parameters (D, E) andgvalues. Ligand‐field theory (LFT) was used to analyze earlier electronic absorption spectra and give calculated ZFS parameters matching those from the experiments. DFT calculations also gave spin densities inCo‐X, showing that the larger Co(II) spin density in a molecule, the larger its ZFS magnitude. The current work reveals dynamics of magnetic and phonon excitations in SMMs. Studies of such couplings in the future would help to understand how spin‐phonon coupling may lead to magnetic relaxation and develop guidance to control such coupling.