Determining conical intersection geometries is of key importance to understanding the photochemical reactivity of molecules. While many small to medium-sized molecules can be treated accurately using multireference approaches, larger molecules require a less computationally demanding approach. In this work, minimum energy crossing point conical intersection geometries for a series of molecules has been studied using spin-flip TDDFT (SF-TDDFT), within the Tamm-Dancoff Approximaton, both with and without explicit calculation of non-adiabatic coupling terms, and compared with both XMS-CASPT2 and CASSCF calculated geometries. The less-computationally demanding algorithms, which do not require explicit calculation of the non-adiabatic coupling terms, generally fare well with the XMS-CASPT2 reference structures, while the relative energetics are only reasonably replicated with the MECP structure calculated with the BHHLYP functional and full non-adiabatic coupling terms. We also demonstrate that, occasionally, CASSCF structures deviate quantitatively from the XMS-CASPT2 structures, showing the importance of including dynamical correlation.

Organofunctionalization of polyoxometalates (POMs) allows the preparation of hybrid molecular systems with tunable electronic properties. Currently, there are only a handful of approaches that allow for the fine-tuning of POM frontier molecular orbitals in a predictable manner. Herein, we demonstrate a new functionalization method for the Wells−Dawson polyoxotungstate [P 2 W 18 O 62 ] 6− using arylarsonic acids which enables modulation of the redox and photochemical properties. Arylarsonic groups facilitate orbital mixing between the organic and inorganic moieties, and the nature of the organic substituents significantly impacts the redox potentials of the POM core. The photochemical response of the hybrid POMs correlates with their computed and experimentally estimated lowest unoccupied molecular orbital energies, and the arylarsonic hybrids are found to exhibit increased visible light photosensitivity comparable with that of arylphosphonic analogues. Arylarsonic hybridization offers a route to stable and tunable organic−inorganic hybrid systems for a range of redox and photochemical applications.

A mixed‐addenda W/Mo hybrid polyoxometalate cluster – K6[P2W15Mo2O61(POC6H5)2] (1) was synthesised from the condensation of K10[P2W15Mo2O61] and PO3C6H7 under acidic conditions. Single‐crystal X‐ray diffraction confirmed the structure of the hybrid cluster and the presence of two Mo centres in the cap of the lacunary cluster. The electronic effects of metal substitution were studied by cyclic voltammetry, spectroelectrochemistry and electron paramagnetic resonance spectroscopy and supported by density functional theory calculations. Comparing 1 to its tungsten‐only analogue K6[P2W17O61(POC6H5)2] (2), a more positive potential for the first reduction process was induced by the substitution of W for Mo, consistent with a significant lowering of the cluster LUMO energy.

Herein, we report the synthesis and characterization of a new class of hybrid Wells–Dawson polyoxometalate (POM) containing a diphosphoryl group (P2O6X) of the general formula [P2W17O57(P2O6X)]6− (X=O, NH, or CR1R2). Modifying the bridging unit X was found to impact the redox potentials of the POM. The ease with which a range of α‐functionalized diphosphonic acids (X=CR1R2) can be prepared provides possibilities to access diverse functionalized hybrid POMs. Compared to existing phosphonate hybrid Wells–Dawson POMs, diphosphoryl‐substituted POMs offer a wider tunable redox window and enhanced hydrolytic stability. This study provides a basis for the rational design and synthesis of next‐generation hybrid Wells–Dawson POMs.

Derivatives of the widely used 1,6-diphenyl-1,3,5-hexatriene have been considered using spin-flip time-dependent density functional theory, classical molecular dynamics and hybrid quantum mechanics / molecular mechanics. We identify a potential probe...