Synthetic Assembly of Inorganic-organic Polyoxometalate Hybrid Structures Employing Noncovalent Interactions between 5,6-Substituted 1,10-Phenanthroline Derivative Ligands

A new strategy for the synthesis of polyoxometalate-based （POM-based） metal- organic materials was developed. The approach takes the advantage of the ability of phenanthroline derivative base to build strong noncovalent interactions. Three POM-based metal-organic com- pounds, [Mn（MOPIP）2（OH）2][Mn（MOPIP）2（OH）（SiW12O40）]·6H2O （1）, [Cu2（MOPIP）2（OH）2（H2O）]2-（SiW12O40）·5H2O （2） and [Co（Mo2O7）（MOPIP）]n （3） （MOPIP = 2-（4-methoxyphenyl）-1H-imida- zo[4,5-f][1,10]phenanthroline）, were synthesized under hydrothermal conditions. Single-crystal X-ray analysis reveals that compound 1 displays a mononuclear cluster. These clusters are intercon- nected by a framework of π…π stacking interactions to from a chain and layer structure. Compound 2 shows a multinuclear cluster with Keggin-type polyoxoanions [SiW12O40]^4- as building blocks. Strong hydrogen bonding interactions extend these multinuclear clusters into a two-dimensional layer. Compound 3 is a coordination polymer, in which [Mo2O7]^2- polyoxoanions connect the Co（II） ions running along the direction of one of the crystallographic axes to from a linear chain. Adjacent chains are further assembled into a two-dimensional network by strong hydrogen bonding interactions. The main structural traits in all of the compounds are that polyoxometalate acts as inorganic building blocks and connect metal ions to form cluster structure and coordination polymer. In addition, the photocatalytic activities and mechanism of compounds 1～3 on the degradation of Rhodamine B （RhB） under UV irradiation have been investigated in detail.