A series of POM-based compounds constructed by mono- and mixed-ligands synergetically: structures, electrochemical and selective photocatalytic properties

By using pyrazine (pz) and its derivatives 2,3-naphthalenylphenazine (npz) and 2,3-diphenylpyrazine (dpz), one Lindqvist- and six Keggin-based compounds, [Ag I 2 (npz) 4 (W 6 O 19 )]·npz ( 1 ), [Ag I 2 (npz) 3 (HPW 12 O 40 )] ( 2 ), [Ag I 3 (npz) 4 -(PMo 12 O 40 )] ( 3 ), [Ag I 4 (pz) 5 (SiMo 12 O 40 )] ( 4 ), [Ag I 4 (npz) 2 (pz)(PMo V Mo 11 VI O 40 )] ( 5 ), [Ag I 4 (npz) 4 (dpz) 2 (H 2 O) 2 (SiW 12 O 40 )] ( 6 ) and {Ag I 5 K I 2 (npz) 4 (dpz) 2 [H(PW V W 11 VI O 40 ) 2 ]} ( 7 ), have been hydrothermally synthesized and characterized by single-crystal X-ray diffraction analyses. In compound 1 , there is a distorted “I”-type [Ag(npz) 2 ] + subunit with two npz arranging vertically. Two [Ag(npz) 2 ] + subunits support the [W 6 O 19 ] 2− anion symmetrically. In compound 2 , there are [Ag 2 -(npz) 3 ] 2+ clusters with one linking and two terminate npz, which are further linked by [PW 12 O 40 ] 3− anions to form a “sunrise”-like chain. In compound 3 , there exist a discrete [Ag 2 (npz) 3 ] 2+ cluster and a mono-supporting anion [Ag I (npz)- (HPW 12 O 40 )] − . In compound 4 , there are two kinds of cycles in honeycomb-like Ag-pz layer: six-membered cycle I and eight-membered cycle II. An anion dimmer linked by a Ag I ion embeds in bigger cycle II. In compound 5 , one pz and two npz are connected by four Ag I ions to build a linear [Ag 4 (npz) 2 (pz)] 4+ subunit. The PMo 12 anions link the linear subunits alternately and a 1D chain is formed. In compound 6 , there exists discrete [Ag 2 (npz) 2 (dpz)(H 2 O)] 2+ subunit and Keggin anion. In compound 7 , the Keggin-K inorganic chains are connected by Ag I -npz-dpz subunits to form a 2D layer. The adjacent layers are further linked by anions to build a 3D framework. Moreover, we also have investigated the electrochemical and photocatalytic properties of 1 -- 7 .