Synergetic Spin-Crossover and Luminescent Properties in a Multifunctional 2D Iron(II) Coordination Polymer

We designed and synthesized a strong fluorescent tetradentate pyridine ligand, 3,6,11,12-tetra(pyridin-4-yl)dibenzo[a,c]phenazine (TPDP), by covalently grafting pyridyl to fluorescent dye dbpz, which can react with the Fe(NCX)(2) (X = S and Se) unit, obtaining two new 2D [4 x 4] square-grid compounds, namely, {Fe-II(TPDP)(2)(SCN)(2)middot CHCl(3)middot4CH(3)OH}(n) (1) and {[Fe-II(TPDP)(2)(SeCN)(2)]middotCH(2)Cl(2)middot4CH(3)OH}(n) (2). Both of them show expected one-step spin-crossover (SCO) properties, and complex 2(vacuum) exhibits a combination of the SCO phenomenon and fluorescence in a synergetic way. The energy transfer mechanism of 2(vacuum) is verified by the theoretical calculations and experimental results. This study provides an effective strategy to synthesize large conjugated fluorescent ligands using dyes to further form SCO-luminescent bifunctional materials.