Design and Assembly of Covalently Functionalised Polyoxofluorovanadate Molecular Hybrids

Abstract

Mixed-valent polyoxometalate (POM) clusters are one of the most interesting host species, showing a wide range of structural features and properties. The facile preparation and functionalisation of a mixed-valent polyoxofluorovanadates is reported, where two electrons are trapped to antipodal sites of the clusters. The first members of this family of clusters with the general formula, [V V O (μ-O) (μ -O) (μ -F) (L) ] , where L: py=pyridine (1); pyr=pyrazine (2); im=imidazole (3), are unique organic-inorganic hybrids with the addition of a N-donor ligand at either end of the polyoxofluorovanadate. The composition and connectivity of 1-3 were characterised by single-crystal X-ray diffraction and electrospray ionisation mass spectrometry. Electron paramagnetic resonance spectroscopy revealed that the two well-separated V ions in each cluster are fully uncoupled with J=0, giving a degenerate singlet-triplet ground state. This attenuation of the exchange interaction is probed with density functional theoretical calculations that reveal that the inclusion of the fluoride ion in the cluster produces a bond pathway biased toward destructive interference between competing ferromagnetic and antiferromagnetic interactions. These robust molecular materials are the ideal combination of desirable electronic properties, with an organic handle with which they can be integrated into spintronic circuitry for molecular devices.

Synthesis and oxidation catalysis of a difluoride-incorporated polyoxovanadate and isolation of active vanadium alkylperoxo species

“…The reactivity of V12-OO t Bu was quite different from that of (dipic)VO(OO t Bu). 55 The 51 V and 19 F NMR spectra of the reaction solution after the reaction were identical to those of V12-O t Bu, without the formation of any other species (Fig. S2 †).…”

“…44 In the presence of t BuOH, the addition of p-toluenesulfonic acid (TsOH) to the V11 solution gave a new signal set at −460, −473, −486, −523, −545, and −582 ppm with an intensity ratio of 2 : 1 : 1 : 1 : 4 : 2 : 1 (Fig. 2) in 51 V NMR. The 19 F NMR spectrum showed two peaks at −59 and −63 ppm (Fig.…”

“…S12 †). 51 V NMR: δ −460, −473, −486, −523, −545 and −582 ppm. 19 All procedures were carried out under N 2 .…”

“…The required amount of additives was added to a 17 mM of acetonitrile solution of V12-O t Bu. From the intensity ratio of the two peaks at the higher magnetic field in 51 V NMR spectra, the molar ratio of V12-O t Bu and the ligand-exchange product was determined. The equilibrium constant for the following reaction of V12-O t Bu and coordinative reactant (LH) to form the ligand exchange product (V12-L) and t BuOH was calculated.…”

“…42 On the other hand, the chemistry of fluoride-incorporated polyoxovanadates is noteworthy. 34,[43][44][45][46][47][48][49][50][51][52][53] While usual polyoxovanadates with anion templates possess single anions surrounded by only square pyramids, most fluorideincorporated polyoxovanadates possess two fluoride inside the spheres. Furthermore, some of these fluorideincorporated polyoxovandates adopt coordination environments of tetrahedra, trigonal by-pyramids in addition to square pyramids (Table S2 †).…”