Tetraethylammonium dicyanido(5,10,15,20-tetraphenylporphyrinato)ferrate(III) dichloromethane monosolvate

The title compound, (C8H20N)[Fe(C44H28N4)(CN)2]·CH2Cl2 or (Et4N)[Fe(TPP)(CN)2], was recrystallized from dichloromethane–diethyl ether. The compound crystallizes with the two unique halves of the FeIII porphyrinato complex, one tetraethylammonium cation and one interstitial dichloromethane molecule within the asymmetric unit. Both anionic FeIII complexes exhibit inversion symmetry. Both the cation and the solvent molecules show positional disorder. The cation is disordered over two sets of sites with an occupancy ratio of 0.710 (3):0.290 (3); the solvent molecule is disordered over three positions with a 0.584 (6):0.208 (3):0.202 (5) ratio. The crystal packing features columns of [Fe(TPP)(CN)2]− anions that propagate along [001]. The columns further pack into layers that are parallel to (011) and also include the Et4N+ cations. The interstitial CH2Cl2 molecules appear in the interlayer space. This complex may serve as a useful precursor for the assembly of multinuclear and extended CN-bridged complexes for the design of single-molecule and single-chain magnets, respectively

Preparation, Properties and Crystal Structure of \u3cem\u3eSyn\u3c/em\u3e-Isomer of 2,6-Dichlorophenyl-Cyanoxime, H(2,6-diCl-PhCO): Potent \u3cem\u3eCarbonyl Reductase\u3c/em\u3e Inhibitor

The oximino(2,6-dichlorophenyl)acetonitrile, H(2,6-diCl-PhCO) has been synthesized in a reasonably high yield of 60%, and characterized using a variety of physical, electrochemical, spectroscopic methods and X-ray analysis. This compound belongs to the family of cyanoximes; a new subclass of oximes with the general formula NC–C(=N–OH)–R (where R is an electron-withdrawing group) which recently emerged as new biologically active compounds. This cyanoxime represents a disubstituted arylcyanoxime that was found to be a powerful inhibitor of the Carbonyl Reductase enzyme involved in the developing of resistance to anticancer treatment, and the making of cardiotoxic derivatives of anthracyclines that are currently used in medicine. The oximino(2,6-dichlorophenyl)acetonitrile, H(2,6-diCl-PhCO) is a weak acid with pKa = 6.17 and does not dissociate in organic polar protic and aprotic solvents. The cyanoxime was obtained as a microcrystalline mixture of two diastereomers (anti- and syn-) and deprotonates in solutions with the formation of yellow anions which exhibit solvatochromic behavior. However, one specific diastereomer—syn—was isolated in crystalline form from a solvent system as colorless blocks overlayed with pentane ether solution in a monoclinic system in a P2/c (#13) space group with unit cell parameters:  = 8.1720(2),  = 8.8013(3),  = 13.0146(4) and β = 102.546(3); Z = 4. A single crystal was studied using filtered CuKa radiation, providing Rint value of 0.0348 from a full-sphere of reflections. A crystal structure was solved using direct methods, and well refined to R1 = 0.0459, wR2 = 0.1268 and GOF = 1.107. The studied specimen of oximino(2,6-dichlorophenyl)acetonitrile, H(2,6-diCl-PhCO), represents a highly non-planar, rare syn-diastereomer in which the oxime fragment is positioned towards the chlorinated phenyl group. In the crystal, the compound forms a columnar structure extended along the c-direction by using slipped π–π stacking interactions. Columns are interconnected via H-bonding between the oxime OH-group and N atom of the nitrile group with the following parameters: N–H = 1.841 Å, and 169.20° N···H–O angle. No thermal interconversion of syn- into anti- diastereomer was observed upon heating of crystals of one isomer under flow of Ar

Spin crossover in Fe(II) complexes with N₄S₂ coordination

Reactions of Fe­(II) precursors with the tetradentate ligand <i>S,S</i>′-bis­(2-pyridylmethyl)-1,2-thioethane (bpte) and monodentate NCE^– coligands afforded mononuclear complexes [Fe­(bpte)­(NCE)₂] (<b>1</b>, E = S; <b>2</b>, E = Se; <b>3</b>, E = BH₃) that exhibit temperature-induced spin crossover (SCO). As the ligand field strength increases from NCS^– to NCSe^– to NCBH₃^–, the SCO shifts to higher temperatures. Complex <b>1</b> exhibits only a partial (15%) conversion from the high-spin (HS) to the low-spin (LS) state, with an onset around 100 K. Complex <b>3</b> exhibits a complete SCO with <i>T</i>_1/2 = 243 K. While the γ-<b>2</b> polymorph also shows the complete SCO with <i>T</i>_1/2 = 192 K, the α-<b>2</b> polymorph exhibits a two-step SCO with the first step leading to a 50% HS → LS conversion with <i>T</i>_1/2 = 120 K and the second step proceeding incompletely in the 80–50 K range. The amount of residual HS fraction of α-<b>2</b> that remains below 60 K depends on the cooling rate. Fast flash-cooling allows trapping of as much as 45% of the HS fraction, while slow cooling leads to a 14% residual HS fraction. The slowly cooled sample of α-<b>2</b> was subjected to irradiation in the magnetometer cavity resulting in a light-induced excited spin state trapping (LIESST) effect. As demonstrated by Mössbauer spectroscopy, an HS fraction of up to 85% could be achieved by irradiation at 4.2 K

Spin Crossover in Tetranuclear Fe(II) Complexes, {[(tpma)Fe(μ-CN)]₄}X₄ (X = ClO₄^–, BF₄^–)

Two Fe­(II) complexes, {[(tpma)­Fe­(μ-CN)]₄}­X₄ (X = ClO₄^– (<b>1a</b>), BF₄^– (<b>1b</b>); tpma = tris­(2-pyridylmethyl)­amine), were prepared by reacting the {Fe­(tpma)}²⁺ building block with (Bu₄N)­CN. The crystal structures of <b>1a</b> and <b>1b</b> feature a tetranuclear cation composed of cyanide-bridged Fe­(II) ions, each capped with a tetradentate tpma ligand. The Fe₄(μ-CN)₄ core of the complex is strongly distorted, assuming a butterfly-like geometry. Both complexes exhibit gradual temperature-driven spin crossover (SCO) associated with the high-spin (HS) ↔ low-spin (LS) transition at two out of four metal centers. The evolution of HS and LS Fe­(II) ions with temperature was followed by a combination of X-ray crystallography, magnetic measurements, and Mössbauer spectroscopy. Only the Fe­(II) ions surrounded by six N atoms undergo the SCO. A comparison of the temperature-dependent SCO curves for the samples stored under solvent and the dried samples shows that the former exhibit a much more abrupt SCO. This finding was interpreted in terms of the increased structural disorder and decreased crystallinity caused by the loss of the interstitial solvent molecules in the dried samples

Spin Crossover in Fe(II) Complexes with N₄S₂ Coordination

Reactions of Fe­(II) precursors with the tetradentate ligand <i>S,S</i>′-bis­(2-pyridylmethyl)-1,2-thioethane (bpte) and monodentate NCE^– coligands afforded mononuclear complexes [Fe­(bpte)­(NCE)₂] (<b>1</b>, E = S; <b>2</b>, E = Se; <b>3</b>, E = BH₃) that exhibit temperature-induced spin crossover (SCO). As the ligand field strength increases from NCS^– to NCSe^– to NCBH₃^–, the SCO shifts to higher temperatures. Complex <b>1</b> exhibits only a partial (15%) conversion from the high-spin (HS) to the low-spin (LS) state, with an onset around 100 K. Complex <b>3</b> exhibits a complete SCO with <i>T</i>_1/2 = 243 K. While the γ-<b>2</b> polymorph also shows the complete SCO with <i>T</i>_1/2 = 192 K, the α-<b>2</b> polymorph exhibits a two-step SCO with the first step leading to a 50% HS → LS conversion with <i>T</i>_1/2 = 120 K and the second step proceeding incompletely in the 80–50 K range. The amount of residual HS fraction of α-<b>2</b> that remains below 60 K depends on the cooling rate. Fast flash-cooling allows trapping of as much as 45% of the HS fraction, while slow cooling leads to a 14% residual HS fraction. The slowly cooled sample of α-<b>2</b> was subjected to irradiation in the magnetometer cavity resulting in a light-induced excited spin state trapping (LIESST) effect. As demonstrated by Mössbauer spectroscopy, an HS fraction of up to 85% could be achieved by irradiation at 4.2 K