Asymmetrical Polar Modification of a Bivanadium-Capped Keggin POM by Multiple Cu−N Coordination Polymeric Chains

An unprecedented asymmetrically modified bivanadium-capped Keggin polyoxometalate (POM), {AsMo12O40(VO)[VO(H2O)]}·[Cu(4,4‘-bipy)]5·H2O (1) (bipy = bipyridine), has been hydrothermally synthesized and structurally
characterized by a routine technique. Single-crystal X-ray diffraction analysis reveals that compound 1 exhibits a
unique (3,4,6)-connected 3D framework with a (62·81)2(83)2(64·82)2(61·814) topology, constructed from
{AsMo12O40(VO)[VO(H2O)]}5- polyoxoanions modified by six {Cu(bipy)}n coordination polymeric chains. The
asymmetrical polar coordination mode has never been found in the POM chemistry hitherto. It is also the first
example of the bivanadium-capped POM as an anionic template to construct a 3D framework with the highest
connection number of bicapped POMs. Additionally, by just changing the length of the organic ligand, a new
compound {[AsMo12O40(VO)2][Cu(bpe)]2}·[Cu(bpe)]·[H2bpe]·H2O (2) (bpe = bis(4-pyridyl)ethylene), has been
obtained, in which the {AsMo12O40(VO)2} sections are modified by double monotrack {Cu(bpe)}n coordination
polymeric chains to form a “rail-like” 1D structure.