Absorption of Water Vapor by Bambus[6]uril and a Density Functional Theory Study of Its Aqua Complexes.

The absorption/desorption of water vapor by bambus[6]uril (Bu[6]) has been studied. According to kinetic experiments, the absorption capacity of Bu[6] is 4 moles of water per 1 mole of Bu[6] with the absorption duration of 20 min and the complete desorption duration of 100 min. Experimental rate constants for water vapor absorption and desorption by Bu[6] have been determined to be 0.166 min-1 and 0.0221 min-1, respectively. The obtained results are in agreement with theoretical calculations using the DFT method. A hypothetical structure of bambus[6]uril tetrahydrate (Bu[6]·4H2O) has been proposed based on the experimental and DFT data.

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(-) (1a), BF4(-) (1b); tpma = tris(2-pyridylmethyl)amine), were prepared by reacting the {Fe(tpma)}(2+) building block with (Bu4N)CN. The crystal structures of 1a and 1b 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.

Tetra-ethyl-ammonium dicyanido(5,10,15,20-tetra-phenyl-porphyrinato)ferrate(III) di-chloro-methane monosolvate.

The title compound, (C8H20N)[Fe(C44H28N4)(CN)2]·CH2Cl2 or (Et4N)[Fe(TPP)(CN)2], was recrystallized from di-chloro-methane-diethyl ether. The compound crystallizes with the two unique halves of the Fe(III) porphyrinato complex, one tetra-ethyl-ammonium cation and one inter-stitial di-chloro-methane mol-ecule within the asymmetric unit. Both anionic Fe(III) complexes exhibit inversion symmetry. Both the cation and the solvent mol-ecules 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 mol-ecule 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 inter-stitial CH2Cl2 mol-ecules appear in the inter-layer space. This complex may serve as a useful precursor for the assembly of multinuclear and extended CN-bridged complexes for the design of single-mol-ecule and single-chain magnets, respectively.