Spin Crossover Quenching by "Racemization" in a Family of -1,2-Di(tetrazol-1-yl)cyclopentane-Based Fe(II) 1D Coordination Polymers.

Optically pure ()- and racemic (/)--1,2-di(tetrazol-1-yl)cyclopentane were synthesized and used to prepare homo- and heterochiral Fe(II) coordination compounds. [Fe((/)-CHN)(CHCN)](BF) (), [Fe((/)-CHN)(CHCN)](BF) (), [Fe(()-CHN)(CHCN)](BF)·2CHCN (), and [Fe(()-CHN)(CHCN)](BF) () form a family of one-dimensional coordination polymers. Fe(II) cations in these complexes are characterized by a heteroleptic coordination environment: the neighboring metal centers are bridged by two 1,2-di(tetrazol-1-yl)cyclopentane molecules, while the nitrile molecules (acetonitrile or propionitrile, respectively) occupy the axial positions.

Expanding the dimensionality of bis(tetrazolyl)alkane-based Fe(II) coordination polymers by the application of dinitrile coligands.

Reactions between 1,2-di(tetrazol-2-yl)ethane (ebtz), 1,6-di(tetrazol-2-yl)hexane (hbtz) or 1,1'-di(tetrazol-1-yl)methane (1ditz) and Fe(BF) in the presence of adiponitrile (ADN), glutaronitrile (GLN) or suberonitrile (SUN) resulted in the formation of coordination polymers [Fe(μ-ebtz)(μ-ADN)](BF) (1), [Fe(μ-hbtz)(μ-ADN)](BF) (2), [Fe(μ-1ditz)(GLN)](BF)·GLN (3) and [Fe(μ-1ditz)(μ-SUN)](BF)·SUN (4). It was established that the application of dinitriles allows an increase in the dimensionality of the ebtz and hbtz based systems while maintaining the structure of the polymeric units characteristic of previously studied mononitrile based analogues. In 3 and 4, regardless of the type of dinitrile coligand, the motif of 2D polymeric layers constituted by 1ditz molecules remains preserved.

Extremely Slow Thermally-Induced Spin Crossover in the Two-Dimensional Network [Fe(bbtr) ](BF ).

Cooling [Fe(bbtr) ](BF ) (bbtr=1,4-di(1,2,3-triazol-1-yl)butane) triggers very slow spin crossover below 80 K (T =76 K). The spin crossover (SCO) is accompanied by a hysteresis loop (T =89 K). In contrast to isostructural perchlorate analogue [Fe(bbtr) ](ClO ) in which spin crossover during cooling is preceded by phase transition at T =126 K in tetrafluoroborate phase transition does not occur to the beginning of spin crossover (80 K).

Synergic Effect of Phthalide Lactones and Fluconazole and Its New Analogues as a Factor Limiting the Use of Azole Drugs against Candidiasis.

The resistance of and other pathogenic yeasts to azole antifungal drugs has increased rapidly in recent years and is a significant problem in clinical therapy. The current state of pharmacological knowledge precludes the withdrawal of azole drugs, as no other active substances have yet been developed that could effectively replace them. Therefore, one of the anti-yeast strategies may be therapies that can rely on the synergistic action of natural compounds and azoles, limiting the use of azole drugs against candidiasis.

Single crystal-to-single crystal transformation - from two distinct to three distinct spin crossover centers in 2D coordination polymer [Fe(bbtr)](CFSO).

1,4-Di(1,2,3-triazol-1-yl)butane (bbtr) forms a two-dimensional (2D) coordination polymer (1) in a reaction with iron(II) triflate. In the crystal lattice there are two crystallographically unique iron(II) ions surrounded octahedrally by a 1,2,3-triazole ring coordinated through nitrogen atoms N3. Single crystal X-ray diffraction studies revealed that spin crossover for each crystallographically independent iron(II) ion proceeds at a different temperature ((Fe1) = 201 K; (Fe2) = 216 K), while the magnetic measurements showed that there is one step, complete thermally induced spin crossover ( = 205 K).

The first amino acid bound manganese-calcium clusters: a {[MnCa]} methylalanine complex, and a [MnCa] trigonal prism.

An amino acid containing octanuclear heterometallic {[MnCa]} cluster has been synthesized, alongside a structurally-related trigonal prismatic [MnCa] cage.

Spatiotemporal Studies of the One-Dimensional Coordination Polymer [Fe(ebtz) (C H CN) ](BF ) : Tug of War between the Nitrile Reorientation Versus Crystal Lattice as a Tool for Tuning the Spin Crossover Properties*.

Reaction of 1,2-di(tetrazol-2-yl)ethane (ebtz) with Fe(BF ) ⋅6 H O in different nitriles yields one-dimensional coordination polymers [Fe(ebtz) (RCN) ](BF ) ⋅nRCN (n=2 for R=CH (1) and n=0 for R=C H (2) C H (3), C H (4), CH Cl (5)) exhibiting spin crossover (SCO). SCO in 1 and 3-5 is complete and occurs above 160 K. In 2, it is shifted to lower temperatures and is accompanied by wide hysteresis (T =78 K, T =123 K) and proceeds extremely slowly.

Two ways of spin crossover in an iron(ii) coordination polymer associated with conformational changes of a bridging ligand.

1,4-Di(1-ethyl-1,2,3-triazol-5-yl)butane (bbtre) was prepared by lithiation of 1-ethyl-1,2,3-triazole, followed by alkylation with 1,4-dibromobutane. The ligand bbtre forms a three-dimensional network with Fe(ii), [Fe(bbtre)3](ClO4)2·2CH3CN, that exhibits thermally induced spin crossover (SCO). A change of temperature or change of spin state results in various types of structural transformation, leading to different structures that are stable in strictly defined temperature ranges.

Structures and Spectral and Magnetic Properties of a Series of Carbacylamidophosphate Pentanuclear Lanthanide(III) Hydroxo Complexes.

A series of pentanuclear lanthanide complexes LnL(μ-L)(μ-OH)(μ-OH) (Ln = Nd, Dy, Ho, Er, Yb; L = dimethyl -benzoylamidophosphate ion, [CHC(O)-N-P(O)(OCH)]) was obtained by the reaction of sodium dimethyl -benzoylamidophosphate with the corresponding lanthanide nitrates. The pentanuclear cores formed as a result of self-arrangement and their composition did not depend on the lanthanide ion. The complexes and sodium dimethyl -benzoylamidophosphate have been characterized by single-crystal X-ray diffraction.

Magnetic dimensionality and the crystal structure of two copper(ii) coordination polymers containing Cu and Cu building units.

The electrostatic self-assembly reaction of the [Cu(HL)] cation, where HL = 2-(2-aminoethylamino) ethanol, and the N or [Fe(CN)] anion leads to the formation of two coordination polymers with the general formula of [Cu(μ-N)(μ-N)(μ-N)(μ-N)(HL)] (1) and {[Cu(HL)][Fe(CN)]·HO} (2), respectively. The resulting compounds have been structurally characterized by a single-crystal X-ray diffraction technique. Compound 1 possesses a rare 3D structure.

Dinuclear and Mononuclear Rhenium Coordination Compounds upon Employment of a Schiff-Base Triol Ligand: Structural, Magnetic, and Computational Studies.

The 1:1 reaction of trans-[ReCl(PPh)(MeCN)] with 2-(β-naphthalideneamino)-2-hydroxymethyl-1-propanol, HL, in toluene gave the dinuclear complex [ReCl(HL)(PPh)]·2CH (1·2CH), while the 1:2 reaction led to the formation of complex [ReCl(HL)(PPh)] (2). In both species, the Schiff-base ligand exists in its doubly deprotonated form, HL, forming chelate rings around the metallic centers. In addition, 1·2CH displays a unique triple metal-to-metal bond between the two trivalent rhenium ions separated at a 2.

"Normal" and "reverse" spin crossover induced by two different structural events in iron(ii) coordination polymer.

In [Fe(ebbtr)2(CH3CN)2](CF3SO3)2·4CH3CN spin crossover is associated with the occurrence of "normal" and "reverse" hysteresis loops separated by a region of stable HS form. This results from trans-trans → gauche-trans conformational changes of ebbtr molecules and anion reorientation, which occur in different ways during cooling and during heating.

Fermentation parameters and conditions affecting levan production and its potential applications in cosmetics.

Levan is a polysaccharide composed of fructose units with β-2,6-glycoside bonds. Microorganisms synthesize levan by levansucrase as a mixture of low- and high-molecular-weight fractions. Due to its properties, it has a wide range of applications in cosmetics, pharmaceuticals, food and medicine; it appears that the molecular weight of levan might impact its industrial use.

Sliding Polymeric Layers and Anion Displacement Coupled with Spin Crossover in Two-Dimensional Networks of [Fe(hbtz) (CH CN) ](BF ).

The abrupt high spin (HS)→low spin (LS) transition (T =136 K) in [Fe(hbtz) (CH CN) ](BF ) (hbtz=1,6-di(tetrazol-2-yl)hexane) is finished at 100 K and further thermal treatment influences the spin crossover. Subsequent heating involves a change of the spin state in the same way (T =136 K) on cooling. In contrast, cooling below 100 K triggers different behavior and T is shifted to 170 K.

Double spin transition in a two dimensional Fe(ii) coordination network.

In the two dimensional network [Fe(ebbtr)2(CH3CN)2](ClO4)2·4CH3CN a sequence of LS → HS → LS → HS transitions occurs as the exclusive result of the change in temperature. This property results from the extraordinary flexibility/elasticity manifested in the hierarchical arrangement of structural events involving the reorientation of coordinated/noncoordinated molecules as well as with the deformation and the mutual shift of the polymeric units.

Synthesis and magneto-structural studies on a new family of carbonato bridged 3d-4f complexes featuring a [CoLn(CO)] (Ln = La, Gd, Tb, Dy and Ho) core: slow magnetic relaxation displayed by the cobalt(ii)-dysprosium(iii) analogue.

A new family of [3 + 3] hexanuclear 3d-4f complexes [(μ-CO){CoLnL(μ-OH)(OH)}]-(ClO)·mCHOH·nHO (1-5) [Ln = La (1), Gd (2), Tb (3), Dy (4), and Ho (5)] have been prepared in moderate to high yields (62-78%) following a self-assembly reaction between the ligand 6,6',6''-(nitrilotris(methylene))tris-(2-methoxy-4-methylphenol) (HL), Co(OAc)·4HO and the lanthanide ion precursors in the mandatory presence of tetrabutylammonium hydroxide. During the reaction, atmospheric carbon dioxide is fixed in the product molecule as a bridging carbonato ligand which connects all the three lanthanide centers of this molecular assembly through a rare η:η:η-μ mode of bridging as revealed from X-ray crystallography. The metal centers in all these compounds, except the Gd analogue (2), are coupled in antiferromagnetic manner while the nature of coupling in the CoGd complex is ferromagnetic.

Physical and Structural Characterization of Imidazolium-Based Organic-Inorganic Hybrid: (C3N2H5)2[CoCl4].

(C3N2H5)2[CoCl4] (ICC) was characterized in a wide temperature range by the single-crystal X-ray diffraction method. Differential scanning calorimetry revealed two structural phase transitions: continuous at 245.5 K (from phase I to II) and a discontinuous one at 234/237 K (cooling/heating) (II → III).

Influence of conformational changes on spin crossover properties and superstructure formation in 2D coordination polymers [Fe(hbtz)2(RCN)2](ClO4)2.

2D structurally related iron(ii) coordination networks {[Fe(hbtz)2(RCN)2](ClO4)2}∞ featuring, besides tetrazol-2-yl rings in the first coordination sphere, also axially coordinated propionitrile or allyl cyanide molecules (R = C3H5-, 1; R = C2H5-, 2) were synthesized. Thermally induced spin crossover (SCO) in 1 takes place in two poorly resolved stages (T(1)1/2(↓) = T(1)1/2(↑) = 198 K, T(2)1/2(↓) = 170 K, T(2)1/2(↑) = 171 K) whereas in 2 complete and relatively gradual one step SCO (T1/2(↓) = T1/2(↑) = 160 K) occurs. Diversification of the SCO properties of the complexes originates from the ability of coordinated allyl cyanide in 1 to undergo conformational alterations, which is not observed for propionitrile molecules in 2.

HS⇄LS transition in iron(II) two-dimensional coordination networks containing tris(tetrazol-1-ylmethyl)methane as triconnected building block.

Novel tripodal ligand 1,1',1''-tris(tetrazol-1-ylmethyl)methane (111tz) and products of its reactions with perchlorate as well as with tetrafluoroborate salts of iron(II) are presented. The isostructural complexes, [Fe(111tz)₂](ClO₄)₂ and [Fe(111tz)₂](BF₄)₂, were isolated as two-dimensional (2D) coordination networks revealing a honeycomb-like pattern with cages occupied by disordered anions. 111tz molecules act as a tridentate ligand bridging three adjacent Fe(II) ions, and the nitrogen N4 atom of six tetrazole rings (tz) is placed in octahedron vertices of FeN₆ chromophores.

Nitrile-rich coordination polymer (1)(∞){[Fe(CH(3)CN)(4)(pyrazine)](ClO(4))(2)} exhibiting a HS ⇆ LS transition.

In a 1D network of (1)(∞){[Fe(CH(3)CN)(4)(pyrazine)](ClO(4))(2)}, the presence of four neutral nitrile molecules besides the pyrazine donors in the first coordination sphere of iron(II) allows one to achieve a ligand field strength appropriate for the "spin-crossover" occurrence.

A new family of spin-crossover complexes based on a FeII(tetrazolyl)4(MeCN)2-type core.

A bitopic ligand 2-hydroxy-1-(tetrazol-1-yl)-3-(tetrazol-2-yl)propane (12pbtzOH) was synthesized and reacted with Fe(ClO4)(2).6H2O, giving a 1D coordination polymer {[Fe(12pbtzOH)2(CH3CN)2](ClO4)(2).2CH3CN} infinity that exhibits a high-spin to low-spin transition (T1/2(downward arrow)=T1/2(upward arrow) congruent with 104 K).