Iron(III) spin-crossover (SCO) complexes [Fe(qsal)]BS·MeOH·HO (1), [Fe(qsal)](NS)·MeOH (2), [Fe(qnal)](NS) (3), and [Fe(qnal)]PS·MeOH·CHCl (4) (Hqsal, N-(8-quinolinyl)salicylaldimine; Hqnal, N-(8-quinolinyl)-2-hydroxy-1-naphthaldimine; BS, benzenesulfonate; NS, 1-naphthalenesulfonate; PS, 1-pyrenesulfonate) have been synthesized and characterized by X-ray structure determinations and temperature-dependent magnetic susceptibility measurements. The aromatic counteranions BS, NS, and PS can be used for the tuning of intermolecular coupling through a variety of weak interactions. All of the complexes show temperature-dependent SCO behavior. but the light-induced excited spin-state trapping (LIESST) effect was observed only for 1, 3, and 4 when the samples were illuminated (λ 808 nm) for 1 h at 5 K. In particular, 59% of the LS form of 1 was converted to the metastable HS state by illumination, equal to the highest degree of conversion yet known for LIESST in [Fe(qsal)] derivatives. The lack of a LIESST effect for 2 may be due to the relatively limited degree of interaction between the cations and anions in the lattice, reflected in a much longer minimum Fe···Fe separation in this complex in comparison to the others.

The development of molecule-based switchable materials remains an important challenge in the field of molecular science. Achievement of a structural phase transition induced by adsorption/desorption of guest molecules in spin crossover (SCO) Co­(II) compounds is of significant interest because of the possibility that the spin state of the magnetic anisotropic high-spin (HS, S = 3/2) and low-spin (LS, S = 1/2) states can be switched via the induced changes in associated intermolecular interactions. In this study, we demonstrated a reversible magnetic switching associated with spin state conversion, along with a single-crystal to single-crystal (SCSC) phase transition induced by dehydration/rehydration. [Co­(terpy)2]­(BF4)2·H2O (1·H2O; terpy = 2,2′:6′,2′′-terpyridine) assembles in the solid state via π–π and CH−π interactions involving adjacent terpyridine cores along the ab direction to form two-dimensional (2D) layered domains. 1·H2O exhibits gradual and incomplete SCO, from fully HS to ca. 0.5 HS, and the field-induced single-molecule magnet (SMM) behavior attributed to the presence of the anisotropic partial high-spin Co­(II) species. 1·H2O undergoes a SCSC transformation accompanied by a change from the tetragonal space group I41/a to P42/n via a dehydration process. Dehydrated 1 exhibits a reverse thermal hysteresis behavior (T 1/2↑ = 287 K; T 1/2↓ = 270 K) in the gradual SCO region from fully HS to ca. 0.5 HS, followed by an ordinary thermal hysteresis (T′1/2↑ = 195 K; T′1/2↓ = 155 K) to fully LS Co­(II). A temperature-dependent single-crystal X-ray structural analysis revealed that the reverse hysteresis can be attributed to an order/disorder structural phase transition of the BF4 – anions involving a symmetry breaking to yield the monoclinic space group P21/n and orbital (angular momentum) transition (LT). Both the SCSC phase transition and magnetic behavior are switchable by dehydration/rehydration processes; thus 1 again adsorbs water at room temperature to give both the original structure and its magnetic behavior.

Luminescent ionic liquids are formed by the melting of tetranuclear rhenium(v) clusters.

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Luminescent ZnII clusters [Zn4L4(μ3‐OMe)2X2] (X=SCN (1), Cl (2), Br (3)) and [Zn7L6(μ3‐OMe)2(μ3‐OH)4]Y2 (Y=I− (4), ClO4− (5)), HL=methyl‐3‐methoxysalicylate, exhibiting blue fluorescence at room temperature (λmax=416≈429 nm, Φem=0.09–0.36) have been synthesised and investigated in detail. In one case the external heavy‐atom effect (EHE) arising the presence of iodide counter anions yielded phosphorescence with a long emission lifetime (λmax=520 nm, τ=95.3 ms) at 77 K. Single‐crystal X‐ray structural analysis and time‐dependent density‐functional theory (TD‐DFT) calculations revealed that their emission origin was attributed to the fluorescence from the singlet ligand‐centred (1LC) excited state, and the phosphorescence observed in 4 was caused by the EHE of counter anions having strong CH−I interactions.

A new example of vapor-induced reversible polarity and ferroelectricity switching system has been demonstrated in mononuclear iron(iii) complexes.

The behavior of single-ion magnets (SIMs) that reflects large distortions of their coordination environments caused by the packing of long alkyl chains for two Co­(II) complexes of the type [Co­(C n -terpy)2]­(BF4)2 (C n -terpy = 4′-alkoxy-2,2’:6′,2″-terpyridine; n = 10 (1), 16 (2)) is reported. 1·2MeOH, which features a highly distorted octahedral high-spin Co­(II) center, exhibits field-induced slow magnetic relaxation under an applied dc field of 1000 Oe. Further detailed analysis of the relaxation process indicated the prevalence of the Raman process at low temperature. Surprisingly, 2 shows a reverse spin transition (rST) and also exhibits remarkable field-induced SIM behavior, revealing the presence of magnetic anisotropy for this high-spin Co­(II) species that is triggered by a structural phase transition. We present here the first examples of the coexistence of field-induced slow magnetic relaxation and rST associated with structural phase transitions involving long-alkyl-chain conformational changes from gauche to anti. These results indicate the prospect of inducing SIM properties in other distorted high-spin Co­(II) species bearing long alkyl chains.

The solubilities of 4,4′-diaminodiphenyl ether (ODA) and pyromellitic dianhydride (PMDA) in supercritical carbon dioxide (scCO2) with N,N-dimethylformamide (DMF) were measured by a semibatch flow method, to accumulate new experimental data and to clarify the entrainer effect of DMF on the solubilities of the monomers of aromatic polyimide in scCO2. All measurements were carried out at 323 K and 20.0 MPa with DMF concentrations from 0 to about 20 mol %. The solubilities of both ODA and PMDA increased dramatically with increasing DMF concentration under our experimental conditions. For example, the addition of about 10 mol % of DMF increased the solubilities of ODA and PMDA to 54- and 115-fold, respectively, as compared to their solubilities in pure scCO2. The experimental results were correlated and predicted by the Peng–Robinson equation of state (PR-EOS). The critical temperatures and pressures of ODA and PMDA were estimated utilizing the group contribution method proposed by Constantinou and Gani, and the solid molar volumes of ODA and PMDA needed for calculation were obtained by the COSMO-RS method. The vapor pressures of ODA and PMDA, which are also required to calculate the solubilities, were obtained by correlating the solubilities of ODA and PMDA in pure CO2. The binary interaction parameters were estimated by correlating the phase equilibria and solubilities for each binary system. The predicted results approximately reproduced the experimental results for the solubilities of ODA in scCO2. As for the solubilities of PMDA, while a large deviation was observed between the predicted and experimental results, the correlated results approximately corresponded to the experimental data.