Rhodamine
6G-Labeled Pyridyl Aroylhydrazone Fe(II)
Complex Exhibiting Synergetic Spin Crossover and Fluorescence
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Abstract
Here,
we use a pyridinecarbaldehyde rhodamine 6G hydrazone ligand
(L) to synthesize an Fe(II) complex <b>1</b> for the search
of new fluorescent-spin crossover (SCO) materials. Single-crystal
structural determinations suggest that the Fe(II) ion is chelated
by two ring-opened ligands (L-o) to form a FeN<sub>4</sub>O<sub>2</sub> coordination environment, and intermolecular π---π contacts
of the xanthene groups connect the adjacent molecules to form a supramolecular
one-dimensional chain. Magnetic susceptibility measurements on complex <b>1</b> show that three-step SCO takes place in the temperature
range of 120–350 K, and its desolvated form <b>1-d</b> exhibits SCO around room temperature (<i>T</i><sub>c</sub>↑ = 343 K and <i>T</i><sub>c</sub>↓ = 303
K) with a wide hysteresis loop of 40 K. Moreover, complex <b>1-d</b> displays light-induced excited spin-state trapping phenomenon. Intriguingly,
the fluorescence intensity of the maximum emission at 560 nm for complex <b>1-d</b> displays discontinuous variation in the range of 250–400
K, indicative of the occurrence of synergetic fluorescence and SCO