A cyanide-bridged [Fe 2 Co 2 ] molecular square complex, {[Fe(Tp)(CN) 3 ] 2 [Co(L) 2 ] 2 }(BF 4 ) 2 •2CH 3 CN•6H 2 O [1;Tp = hydrotris(pyrazol-1-yl)borate and L = bis(1-ethyl-1Himidazol-2-yl)ketone], has been synthesized and characterized fully by single-crystal X-ray diffraction, (photo)magnetic measurements, optical reflectivity, and other physical measurements. 1 exhibits a two-step metal-to-metal electron-transfer (MMET)induced spin transition accompanied by thermal hysteresis (T 1/2 ↑ = 332 and 407 K and T 1/2 ↓ = 320 and 405 K, respectively), converting the low-temperature diamagnetic {Fe II LS −CN−Co III LS } ground state into the high-temperature paramagnetic {Fe III LS − CN−Co II HS } state. Additionally, 1 displays reversible photoinduced MMET under light irradiation (ON mode using 808 nm laser light and OFF mode using 532 nm laser light), as confirmed by optical reflectivity and (photo)magnetic measurements. The photoinduced paramagnetic metastable state relaxes back to the diamagnetic ground state at 91 K (T LIESST = 91 K). Astonishingly, 1 also exhibits a 27 K wide light-induced thermal hysteresis below 100 K. The overall results show that 1 is a multistimuli-responsive bistable material that exhibits reversible switching between the diamagnetic state, {Fe II LS −CN−Co III LS }, and the paramagnetic state, {Fe III LS −CN−Co II HS }, under the application of temperature and light.
A 2D coordination polymer, {[Fe(L) 2 (NCSe) 2 ]•6MeOH•14H 2 O} n (1; L = 2,5-dipyridylethynylene-3,4-ethylenedioxythiophene), has been synthesized based on a redox active luminescence ligand. 1 possesses a 2D [4 × 4] square-grid network where the iron(II) center is in a FeN 6 octahedral coordination environment. 1 displays reversible thermoinduced high-spin (HS; S = 2) to diamagnetic low-spin (LS; S = 0) ON/OFF spin-state switching with a T 1/2 value of 150 K. Interestingly, optical reflectivity and photomagnetic studies at 10 K under light irradiation revealed an efficient conversion to a photoinduced metastable HS excited state from a LS ground state. Remarkably, the photoexcited HS state can be reversibly switched ON and OFF by using 625 and 850 nm light-emitting-diode lights. Intriguingly, the thermal dependence of the luminescence intensity of the maximum emission at 524 nm for 1 shows a minimum at around the spin-crossover (SCO) temperature, indicating a cooperative nature between the SCO and luminescence properties. Theoretical calculations confirmed the above findings.
For the first time, a mononuclear cobalt(ii) complex with dicyanamide coligands exhibiting reversible spin crossover behavior at high temperature is reported.
Herein we report the synthesis and characterization of anionic boron-and carbon-based Kekulédiradicaloids spanned by a p-phenylene bridge. In contrast to Thiele's hydrocarbon, a closed-shell singlet system, they show an appreciable population of the triplet state at room temperature, as evidenced by both NMR and EPR spectroscopy. Moreover, en route to these anionic boronand carbon-based hetero-diradicaloids, the formation of an isolable diamino(4-diarylboryl-phenyl)methyl radical was observed.
The three mononuclear cobalt(II) complexes, [Co(L)(NCX)2] (L = N,N'-di-tert-butyl-2,11-diaza[3,3](2,6)pyridinophane, and X = S (1), Se (2), and [C(CN)2] (3)), have been synthesized and characterized using variable temperature single-crystal X-ray crystallography,...
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