First Non-Centrosymmetric Deca-Vanadoborate with Borate Vacancies, Self-Assembled around a 1,3-Propanediammonium Cation

The first borate-vacant deca-vanadoborate
of formula (NH3CH2CH2CH2NH3)5 [(NH3CH2CH2CH2NH3)­V10B24O66H8]·13.23H2O with an occluded
1,3-propanediammonium cation, using molten
methylboronic acid flux reaction is reported. This cluster lacks four
borate units with respect to all known deca-vanadoborates. It crystallizes
in the orthorhombic P21212
space group which is non-centrosymmetric, leading to the first non-centrosymmetric
deca-vanadoborate reported in the literature. Even though the deca-vanadoborates
formed by 28 borate units have an inner space large enough to host
a molecule, no examples have been reported before. The electronic
properties were studied using electronic spectroscopy, corroborating
a fully reduced species, due to the lack of intervalence charge transfer
transitions in the 1000 to 1500 nm region. The magnetic behavior provided
evidence that the studied cluster presents strong antiferromagnetism
among the ten VIV spin-carriers, with an S = 0 ground state. Using a model considering three different exchange
pathways, three different J values were obtained,
all of them antiferromagnetic in nature.