Crystal Structure and Reversible Photochromism of Pb(II)‐ N , N ‐Dimethylformamide Modified Keggin‐Type Polyoxometalates

Two Pb(II)‐DMF complex modified Keggin‐type polyoxometalate compounds, [Pb(DMF) 7 ] 2 [SiW 12 O 40 ] 2DMF (1) and [Pb(DMF) 4 (H 2 O) 2 ][Pb 2 ( μ 2 ‐DMF) 2 (DMF) 8 ][PW 12 O 40 ] 2 (2) (DMF =  N , N ‐dimethylformamide), have been demonstrated in this work. Both 1 and 2 are characterized by X‐ray single crystal diffraction, Fourier transform infrared (FTIR), and UV–vis spectra, and elemental analyses. The crystal structure analysis indicates that compound 1 is composed of Pb(II)‐DMF complex and Keggin‐type [SiW 12 O 40 ] 4− polyoxoanion, in which the Pb 2+ coordinates to the polyoxoanion by different Pb−O bonds, while compound 2 is composed of [Pb(DMF) 4 (H 2 O) 2 ] 2+ , dimeric [Pb 2 ( μ 2 ‐DMF) 2 (DMF) 8 ] 4+ cations, and two kinds of Keggin‐type [PW 12 O 40 ] 2− polyoxoanions. By ultraviolet irradiation, both 1 and 2 display the reversible color change from white (for 1 ) or light yellow (for 2 ) to blue, which can be applied as new crystalline photochromic materials. Upon heating, the blue color of the two compounds can be recovered within 5 min. The successful syntheses of compounds 1 and 2 provide a new route for the design and synthesis of reversible photochromic crystalline materials.