Photosalient Behavior of Photoreactive Zn(II) Complexes

Abstract

Solids\nshowing unusual and unexpected properties are the key toward\nthe development of new advanced functional materials. Here, we describe\ntwo different types of Zn­(II) complexes obtained from three different\nderivatives of 4-styrylpyridine under the same experimental conditions:\n[Zn₃(cin)₆­(2F-4spy)₂­·Zn₂(cin)₄­(2F-4spy)₂] (<b>1</b>), [Zn₂(cin)₄­(4spy)₂] (<b>2</b>), and [Zn₂(cin)₄­(3F-4spy)₂] (<b>3</b>), where cin = cinnamate, 2F-4spy = 2-fluoro-4′-styrylpyridine\nand 3F-4spy = 3-fluoro-4′-styrylpyridine. Of these <b>1</b> is a photostable inorganic cocrystal comprising a trinuclear Zn­(II)\ncomplex and a paddlewheel Zn­(II) complex, whereas <b>2</b> and <b>3</b> are photoreactive Zn­(II) complexes with paddlewheel structure.\nThe neighboring olefin bonds in the styrylpyridine ligands in <b>2</b> and <b>3</b> are aligned in a head-to-tail manner,\nbut not the olefin bonds in the cinnamate ligands. The distance between\nthe pairs of olefin bonds are 4.348(2) Å in <b>2</b> and\n4.045(2) Å in <b>3</b>. However, they not only undergo\nsolid state photochemical [2 + 2] cycloaddition reaction under UV\nlight but also show the photosalient behavior during the photoreaction.\nAn overall increase in the percentage cell volume of 11.93% and 10.13%\nfor <b>2</b> and <b>3</b>, respectively, during the photoreaction\nappears to indicate a significant anisotropic expansion is responsible\nfor the photosalient effect.