Self-assembly And Properties Of Polyoxometalates-based Compounds Decorated By Transition Metal-Rigid/Flexible Polyazole Organic Subunits

In this paper, fourteen polyoxometalates (POMs)-based compounds decorated bytransition metal-rigid/flexible polyazole organic subunits have been synthesized underhydrothermal conditions and structurally characterized by elemental analyses, IR, TG,PXRD and single crystal X-ray diffractions. The electrochemical, photoluminescence andphotocatalytic properties of these compounds have been studied as well.1. The classical Keggin and Wells-Dawson type POM anions were used as inorganicbuilding units and modified by Cu-rigid ptz organic subunits, resulting in five newPOM-based compounds containing multinuclear Cu clusters. The influences ofcrystallization time and types of the POMs on these POM-based compounds containingmultinuclear units have been discussed.[Cu6I(4-ptz)6][H3PMo12O40]·2H2O (1)[Cu6I(4-ptz)6][H3AsMo12O40]·2H2O (2)[Cu3II(4-ptz)4(As2W18O62)(H2O)7]·16H2O (3)[Cu3II(4-ptz)5(As2W18O62)(H2O)5]·4H2O (4)[Cu3II(3-ptz)4(P2W18O62)(H2O)8]·8H2O (5)(4-ptz=5-(4-pyridyl)-tetrazole,3-ptz=5-(4-pyridyl)-tetrazole)Compounds1and2are isostructural, and they display fascinating2D frameworkscontaining hexanuclear [Cu6I(4-ptz)6] units. The hexa-nuclear [Cu6I(4-ptz)6] subunits areconstructed from five [Cu2N4] units with a cycle connecting cycle mode and furtherconnected by the Cu–N bonds to form a1D chain. The adjacent1D chains are furtherlinked by Keggin anions to construct a intriguing2D network. Compound3exhibits anisolated structure constructed from one Keggin anion [PMo12O40]3–and a trinuclear[Cu3(4-ptz)4(H2O)2] subunit, in which the4-ptz shows single coordination mode.Compound4exhibits a1D chain with a trinuclear [Cu3(4-ptz)5(H2O)2] subunit. In[Cu3(4-ptz)5(H2O)2] subunit, the4-ptz exhibits two kinds of coordination modes. Thoughcompounds3and5are similar, there are some differences of coordination modes of POMsanions and ligands.2. By using Ag ions with strong coordination ability and deverse coordination modeand rigid ptz ligands, six multinuclear POM-based compounds have been hydrothermallysynthesized, in which the multinuclear Ag subunits modify classical Keggin andWells-Dawson anions.[Ag7(4-ptz)5(H2O)2][H2SiMo12O40](6) [Ag8(4-ptz)5(H2O)2][AsW12O40](7)[Ag7(4-ptz)5(H2O)][HAsMo12O40](8)[Ag7(3-ptz)4(NO3)(H2O)][H4P2W18O62]·5H2O (9)[Ag6(3-ptz)4(H2O)2][HPMo12O40]·3H2O (10)[Ag5(4-ptz)4][HPMo12O40]·6H2O (11)Compound6is a3D channel network constructed from multi-nuclear Ag5(ptz)5subunits with pairs of [SiMo12O40]4–polyanions residing in the channels as pentadentateinorganic ligands. Compound7exhibits a3D framework containing hexanuclear subunit[Ag6(ptz)5]+, where [AsW12O40]3–polyanions as hexadentate ligands reside in thisframework. Compound8also exhibits a3D MOF based on multinuclear Ag5(ptz)5subunits,in which the hexadentate [AsMo12O40]3–polyanions incorporate. Compound9exhibits aWells-Dawson based3D framework containing the2D layer of multinuclear cycleconnecting cycle. In compound10, there is an infinite2D layer with multinuclear Ag-ptzbelt in the3D framework. Compound11is a2D network constructed from infinite1DAg-ptz belt and [PMo12O40]3-anions.3. By introducing the unprecedented and flexible bis(pyridyl-tetrazole) ligands intoAg-POM systems, three POM-based compounds containing multinuclear helix/loopstructures were synthesized under hydrothermal conditions.{Ag2(4-bptzb)2(H2O)2[H2PMo12O40]2}·4-bptzb·5H2O (12)[Ag4(3-bptzb)2(PMoVMoVI11O40)]·2H2O (13)Ag3(3-bptzb)2.5(H2O)2[H3P2W18O62](14)4-bptzb=1,4-bis(5-(4-pyridyl)-tetrazolyl)butane3-bptzb=1,4-bis(5-(3-pyridyl)-tetrazolyl)butaneCompound12exhibits a dimeric structure constructed from two Keggin [PMo12O40]3-anions and a binuclear [Ag2(trans-4-bptzb)2]2+subunit. In13, the3-bptzb link AgIions togenerate a3D metal-organic framework (MOF), which contains charming meso-helixchains. The Keggin anions reside in the distorted tetragonal channels of the MOF. Incompound14, the3-bptzb adopt versatile coordination modes linking AgIions to firstlyconstruct loop connecting loop1D chains, which are further linked by {Ag[P2W18O62]}nchains to form a scarce hamburger-style2D sheet. These adjacent sheets are further fusedby3-bptzb ligands to construct a3D framework.