AUTHOR=Qiu Ya-Ru , Cui Long , Ge Jing-Yuan , Kurmoo Mohamedally , Ma Guijun , Su Jian 

TITLE=Iron(II) Spin Crossover Coordination Polymers Derived From a Redox Active Equatorial Tetrathiafulvalene Schiff-Base Ligand

JOURNAL=Frontiers in Chemistry

VOLUME=9

YEAR=2021

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2021.692939

DOI=10.3389/fchem.2021.692939

ISSN=2296-2646

ABSTRACT=<p>Two polymorphic Fe<sup>II</sup> coordination polymers [Fe<sup>II</sup>L (TPPE)<sub>0.5</sub>] <bold>1</bold>) and [(Fe<sup>II</sup><sub>3</sub>L<sub>3</sub> (TPPE)<sub>1.5</sub>)] <bold>2</bold>), were obtained from a redox-active tetrathiafulvalene (TTF) functionalized ligand [H<sub>2</sub>L = 2,2’-(((2-(4,5-bis-(methylthio)-1,3-dithiol-2-ylidene)benzo(d) (1,3) dithiole-5,6-diyl)bis-(azanediyl))bis-(meth anylylidene)) (2E,2E')-bis(3-oxobutanoate)] and a highly luminescent connector {TPPE = 1,1,2,2-tetrakis[4-(pyridine-4-yl)phenyl]-ethene}. Complex <bold>1</bold> has a layered structure where the TPPE uses its four diverging pyridines from the TPPE ligand are coordinated by the <italic>trans</italic> positions to the flat TTF Schiff-base ligand, and complex <bold>2</bold> has an unprecedented catenation of layers within two interpenetrated frameworks. These coordination polymers reserved the redox activity of the TTF unit. Complex <bold>1</bold> shows gradual spin transition behavior without hysteresis. And the fluorescence intensity of TPPE in <bold>1</bold> changes in tandem with the spin crossover (SCO) transition indicating a possible interplay between fluorescence and SCO behavior.</p>