Solvent effects on valence tautomerism: A comparison between the interconversion in solution and solid state

Evangelio, Emi; Rodríguez-Blanco, Clara; Coppel, Yannick; Hendrickson, David N.; Sutter, Jean‐Pascal; Campo, Javier; Ruiz‐Molina, Daniel

doi:10.1016/j.solidstatesciences.2007.11.039

Cited by 48 publications

(44 citation statements)

References 30 publications

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“…Generally, thermodynamic parameters (Δ H =73(5) kJ mol −1 , Δ S =265(17) J mol −1 K −1 ) are larger in solution than the solid state 23. 25, 26 However, the obtained values are significantly larger than expected for a thermally induced transition in VT Co complexes in solution (Δ H= 21–38 kJ mol −1 , Δ S =60–133 J mol −1 K −1 ) 25. Unlike the solid state, the temperature dependence of μ eff for 1 in solution cannot be ascribed exclusively to the equilibrium between the two redox isomers ls‐Co III (Cat)(SQ)↔hs‐Co II (SQ) 2 .…”

Section: Resultsmentioning

confidence: 99%

Modulation of Magnetic Properties at Room Temperature: Coordination‐Induced Valence Tautomerism in a Cobalt Dioxolene Complex

Witt

Heinemann

Sproules

et al. 2014

Chemistry A European J

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The valence-tautomeric six-coordinate complex [Co(tbdiox)2(4-papy)2] (1; tbdiox = redox-active 3,5-di-tert-butyl-o-dioxolene, 4-papy = 4-phenylazopyridine) was synthesized and its electronic structure examined. Whereas 1 shows regular thermally driven valence tautomerism in the solid state, it partially dissociates in solution to form the five-coordinate species [Co(tbdiox)2(4-papy)] (2) and free 4-papy. Species 1 and 2 exhibit different electronic structures-low-spin (ls) Co(III) and high-spin (hs) Co(II), respectively-in solution at room temperature and therefore different magnetic properties. Since 1 and 2 are in an equilibrium that is 4-papy-dependent, the magnetic moment of the solution species can be tuned by means of the ligand content. Thus, the concept of coordination-induced valence tautomerism (CIVT) has been introduced. The electronic structures of 1 and 2 as well as their CIVT were elucidated by X-ray crystallography, electrochemistry, titration experiments, and all variable-temperature SQUID susceptometry, NMR, EPR, and electronic absorption spectroscopy. The experimental findings are strongly supported by broken-symmetry DFT calculations. The magnetic exchange interactions in different types of valence-tautomeric cobalt complexes were explored computationally.

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Section: Resultsmentioning

confidence: 99%

Modulation of Magnetic Properties at Room Temperature: Coordination‐Induced Valence Tautomerism in a Cobalt Dioxolene Complex

Witt

Heinemann

Sproules

et al. 2014

Chemistry A European J

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“…This observation was not surprising since it was expected that free energy of the ET process should be strongly dependent on vibronic coupling with the environment. [20][21][22][23] For this reason we decided to synthesize different 6 ) complex (1, DBCat = 3,5-di-tert-butylcatecolato) which was observed to undergo both entropy driven and optically induced valence tautomerism. The results we obtained for the toluene solvate provide, when compared to those previously reported for other derivatives, [17,18] an intriguing benchmark for the description of these systems.…”

mentioning

confidence: 99%

Complete Direct and Reverse Optically Induced Valence Tautomeric Interconversion in a Cobalt–Dioxolene Complex

Dapporto

Dei

Poneti

et al. 2008

Chemistry A European J

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“…However, during this process, the sample lost its valence tautomeric property and, accordingly, its photo-and thermally-switchable phase transition (Fig. SI1), underlying the fact that valence tautomeric complexes are quite sensitive to their environment 36,39,40 .…”

Section: Magnetic and Photomagnetic Measurementsmentioning

confidence: 99%

Photoswitchable stable charge-distributed states in a new cobalt complex exhibiting photo-induced valence tautomerism

et al. 2015

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We report the synthesis and magnetic and photomagnetic behaviour of a novel valence tautomeric cobalt complex, [Co(3,5-dbbq)2(μ-bpym)] (1) (3,5-dbbq = 3,5-di-tert-butyl-1,2-benzoquinone and μ-bpym = 2,2'-bipyrimidine). The synthesis is performed by reacting Co2(CO)8 and μ-bpym in the presence of the ligand 3,5-dbbq in a mixed solvent under inert atmosphere. The magnetic behavior clearly shows the presence of electron transfer from the catecholate ligand to the cobalt center, producing valence tautomers of [Co(II)(SQ)2] with a transition temperature (T1/2) of 215 K. Photomagnetic studies, performed via both SQUID magnetometry and X-band electron paramagnetic resonance, show the clear presence of photoinduced valence tautomerism, at temperatures considerably higher than previous systems. A metastable charge distribution is observed, strengthening previous investigations on the character of mixed valence ligands. Entropy-driven valence tautomeric interconversion is observed, and drives the transition to the most stable charge distribution. The complex has the ability to coordinate and can be used as a photoswitchable building block, with the photomagnetic characterisation evidencing a metastable state lifetime of the photo-induced valence tautomeric process of ca. 2.9 × 10(4) s below 20 K. The observed yields are higher than ones in similar systems, showing that tiny changes in the molecular structures may have a huge impact.

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Solvent effects on valence tautomerism: A comparison between the interconversion in solution and solid state

Cited by 48 publications

References 30 publications

Modulation of Magnetic Properties at Room Temperature: Coordination‐Induced Valence Tautomerism in a Cobalt Dioxolene Complex

Modulation of Magnetic Properties at Room Temperature: Coordination‐Induced Valence Tautomerism in a Cobalt Dioxolene Complex

Complete Direct and Reverse Optically Induced Valence Tautomeric Interconversion in a Cobalt–Dioxolene Complex

Photoswitchable stable charge-distributed states in a new cobalt complex exhibiting photo-induced valence tautomerism

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