Vladislav V. Gurzhiy

Amine-templated uranyl selenates with chiral [(UO2)2(SeO4)3(H2O)]2– layers: topology, isomerism, structural relationships

Abstract Eleven new amine-templated uranyl selenate hydrates have been prepared by evaporation from aqueous solution of uranyl nitrate, selenic acid and the respective amines. The structures of the compounds have been solved by direct methods and refined using least-squares techniques. Each structure is based upon [(UO2)2(SeO4)3(H2O)]2– layers of corner-sharing UO7 pentagonal bipyramids and SeO4 tetrahedra. The layers are based upon 4- and 6-membered rings arranged in different fashion. In topology I, 6-membered rings form edge-sharing chains, whereas, in topology II, they form corner-sharing chains. Layers with the topology II exist in two geometrical isomers that differ in the system of ‘up’ and ‘down’ orientations of tetrahedra relative to the plane of the layer. There are two isomers, one of which is chiral and the other is achiral. The layers with the topology II are chiral. Chirality is induced by the combination of orientations of tetrahedra and direction of the U → H2O bond. The analysis of the relationships between composition and shape of amine molecules and layer topology reveals two important regularities. 1. Aliphatic components of amine molecules tend to associate with 6-MRs of the inorganic layers. 2. Molecules with longer and spacious aliphatic components favor formation of the layers with topology II, whereas those with shorter aliphatic components prefer layers with the topology I.

Aurophilicity in Action: Fine-Tuning the Gold(I)-Gold(I) Distance in the Excited State To Modulate the Emission in a Series of Dinuclear Homoleptic Gold(I)-NHC Complexes.

The solution-state emission profiles of a series of dinuclear Au(I) complexes 4-6 of the general formula Au2(NHC-(CH2)n-NHC)2Br2, where NHC = N-benzylbenzimidazol-2-ylidene and n = 1-3, were found to be markedly different from each other and dependent on the presence of excess bromide. The addition of excess bromide to the solutions of 4 and 6 leads to red shifts of ca. 60 nm, and in the case of 5, which is nonemissive when neat, green luminescence emerges. A detailed computational study undertaken to rationalize the observed behavior revealed the determining role aurophilicity plays in the photophysics of these compounds, and the formation of exciplexes between the complex cations and solvent molecules or counterions was demonstrated to significantly decrease the Au-Au distance in the triplet excited state. A direct dependence of the emission wavelength on the strength of the intracationic aurophilic contact allows for a controlled manipulation of the emission energy by varying the linker length of a diNHC ligand and by judicial choice of counterions or solvent. Such unique stimuli-responsive solution-state behavior is of interest to prospective applications in medical diagnostics, bioimaging, and sensing. In the solid, the investigated complexes are intensely phosphorescent and, notably, 5 and 6 exhibit reversible luminescent mechanochromism arising from amorphization accompanied by the loss of co-crystallized methanol molecules. The mechano-responsive properties are also likely to be related to changes in bromide coordination and the ensuing alterations of intramolecular aurophilic interactions. Somewhat surprisingly, the photophysics of NHC ligand precursors 2 and 3 is related to the formation of ground-state associates with bromide counterions through hydrogen bonding, whereas 1 does not appear to bind its counterions.

Uranyl selenates with organic templates: Principles of structure and characteristics of self-organization

Basic structural principles of uranyl selenates with organic templates are outlined as follows. In compounds with short chain amine molecules (C:N < 8) the primary role plays the correspondence between topology of inorganic complex (isomerism) and structure and shape of a template. In the structures with long chain molecules (C:N ≤ 8), the molecules are associated to form 2- or 1-dimensional supramolecular templates that are connected with inorganic structure according to the charge density matching principle. Compounds with electro neutral molecules (crown ethers) have composite structure, where bonding between organic and inorganic parts is achieved through hydrogen bonding via intermediate oxonium clusters.

Luminescence Solvato- and Vapochromism of Alkynyl-Phosphine Copper Clusters

The reaction of [Cu(NCMe)4][PF6] with aromatic acetylenes HC2R and triphosphine 1,1,1-tris(diphenylphosphino)methane in the presence of NEt3 results in the formation of hexanuclear Cu(I) clusters with the general formula [Cu6(C2R)4{(PPh2)3CH}2][PF6]2 (R = 4-X-C6H4 (1-5) and C5H4N (6); X = NMe2 (1), OMe (2), H (3), Ph (4), CF3 (5)). The structural motif of the complexes studied consists of a Cu6 metal core supported by two phosphine ligands and stabilized by σ- and π-coordination of the alkynyl fragments (together with coordination of pyridine nitrogen atoms in cluster 6). The solid state structures of complexes 2-6 were determined by single crystal XRD analysis. The structures of the complexes in solution were elucidated by (1)H, (31)P, (1)H-(1)H COSY NMR spectroscopy, and ESI mass spectrometry. Clusters 1-6 exhibit moderately strong phosphorescence in the solid state with quantum yields up to 17%. Complexes 1-5 were found to form solvates (acetone, acetonitrile) in the solid state. The coordination of loosely bound solvent molecules strongly affects emission characteristics and leads to solvato- and vapochromic behavior of the clusters. Thus, solvent-free and acetonitrile solvated forms of 3 demonstrate contrasting emission in orange (615 nm) and blue (475 nm) regions, respectively. The computational studies show that alkynyl-centered IL transitions mixed with those of MLCT between the Cu6 metal core and the ligand environment play a dominant role in the formation of excited states and can be considerably modulated by weakly coordinating solvent molecules leading to luminescence vapochromism.

New supramolecular Au(I)-Cu(I) complex as potential luminescent label for proteins.

A novel supramolecular [Au6Cu2(C2C6H4-4-COONC4H4O2)6(Ph2PC6H4PPh2)3](PF6)2 complex functionalized with a succinimide ester alkynyl substituent has been synthesized and characterized using X-ray crystallography, mass spectrometry, and NMR spectroscopy. Like the other complexes of this class, it demonstrates bright emission in acetone and dichloromethane solutions with the excited state lifetime in a microsecond domain. This complex readily reacts with a surface amine group of proteins/enzymes (human serum albumin (HSA), rabbit anti-HSA antibodies, soybean trypsin inhibitor, and α-chymotrypsin) to give covalent conjugates, which contain up to five molecules of the luminescent label bound to the biomolecule. The conjugates keep a high level of the phosphorescent label emission, but in contrast to the parent complex molecule, display excellent solubility and high stability in physiological media. Investigation of the biological activity of the conjugates also showed that the specific structure of the biomolecules remained nearly unchanged upon bonding with the label, which is indicative of a very prospective of the conjugates application in biomolecular detection.

Weddellite from renal stones: Structure refinement and dependence of crystal chemical features on H2O content

Abstract The refinement of the structures of 17 weddellite crystals [Ca(C2O4)·(2+x)H2O, I4/m, a = 12.329-12.378 Å, c = 7.345-7.366 Å, V = 1117.8-1128.6 Å3], which were taken from the oxalic renal stones of the St. Petersburg (Russian Federation) citizens of both sexes aged from 24 to 65 years, has been carried out by the means of single-crystal X‑ray diffraction (R1 = 0.024-0.057). According to the results of the study, the amount of “zeolitic” water molecules (x) in the structure of weddellite varies from 0.13 to 0.37 pfu. A significant positive correlation between the amount of “zeolitic” water in the structure of weddellite and the closest interatomic distance between coordination water molecules in the large channels (OW1-OW1) was found as well as positive correlation between the value of the a parameter and the average distance of in Ca polyhedron. Obtained linear regression equation: x = 5.43a - 66.80, can be used for determination of the “zeolitic” water amount using the known unit-cell a parameter with mean-root-square error ±0.03 pfu. It was found that the x value for the crystals selected from the “mono-weddellite” stones (x = 0.13-0.24) are at the bottom of the range, thus we can assume that weddellite crystals with fewer “zeolitic” water amounts would be relatively stable. This work expands the knowledge of pathogenic crystal growth processes in living organisms and the development of the theory of oxalate stone formation in humans and animals, and may provide a building block for biomolecular technologies that approach the prevention and treatment of diseases associated with lithiasis.

A stimuli-responsive Au(I) complex based on an aminomethylphosphine template: synthesis, crystalline phases and luminescence properties

Herein we report the synthesis of a stimuli-responsive binuclear Au(I) complex based on the 1,5-bis(p-tolyl)-3,7-bis(pyridine-2-yl)-1,5-diaza-3,7-diphosphacyclooctane ligand, which is a novel template for the design of luminescent metal complexes. In the solid state, the complex obtained gives three different crystalline phases, which were characterized by XRD analysis. It was also found that the crystalline phases can be reversibly interconverted by recrystallization or solvent vapour treatment. The emission of these phases varies in the 500–535 nm range. Quite unexpectedly, the emission energy of these phases is mostly determined by the non-covalent interactions of the solvent molecules with the ligand environment, which have nearly no effect on the Au–Au interactions in the chromophoric centre. The complex obtained demonstrates thermo/solvatochromism to display greenish emission in a DCM matrix and blue emission in an acetone matrix at 77 K, in contrast to the blue emission of the phase containing a DCM molecule and greenish-yellow emission of the acetone solvate in a crystal cell at room temperature. The potentially important role of co-crystallized solvent molecules in the ligand-based emission of the complex obtained is supported by DFT calculations.

Supramolecular Au(I)-Cu(I) Complexes as New Luminescent Labels for Covalent Bioconjugation.

Two new supramolecular organometallic complexes, namely, [Au6Cu2(C2C6H4CHO)6(PPh2C6H4PPh2)3](PF6)2 and [Au6Cu2(C2C6H4NCS)6(PPh2C6H4PPh2)3](PF6)2, with highly reactive aldehyde and isothiocyanate groups have been synthesized and characterized using X-ray crystallography, ESI mass spectrometry, and NMR spectroscopy. The compounds obtained demonstrated bright emission in solution with the excited-state lifetime in microsecond domain both under single- and two-photon excitation. The luminescent complexes were found to be suitable for bioconjugation in aqueous media. In particular, they are able to form the covalent conjugates with proteins of different molecular size (soybean trypsin inhibitor, human serum albumin, rabbit anti-HSA antibodies). The conjugates demonstrated a high level of the phosphorescent emission from the covalently bound label, excellent solubility, and high stability in physiological media. The highest quantum yield, storage stability, and luminance were detected for bioconjugates formed by covalent attachment of the aldehyde-bearing supramolecular Au(I)-Cu(I) complex. The measured biological activity of one of the labeled model proteins clearly showed that introduced label did not prevent the biorecognition and specific protein-protein complex formation that was extremely important for the application of the conjugates in biomolecular detection and imaging.

Symmetry reduction in uranyl compounds with [(UO2)2(TO4)3]2- (T = Se, S, Mo) layers: crystal structures of the new guanidinium uranyl selenate and methylammonium uranyl sulfate

Abstract Single crystals of the new guanidinium uranyl selenate, [CH6N3]2[(UO2)2(SeO4)3] (1), and methylammonium uranyl sulfate, [CH3NH3]2[(UO2)2(SO4)3] (2) have been prepared by isothermal evaporation from aqueous solutions under room-temperature conditions. The crystal structure of 1 has been solved by direct methods [monoclinic, P2, a = 9.9448(15), b = 9.727(2), c = 10.1508(15) Å, β = 90.213(12)°, V = 981.9(3) Å3, Z = 2] and refined to R1 = 0.0696 (wR2 = 0.1611) for 2511 reflections with |F0| ≥ 4σF using least square techniques. The crystal structure of 2 has been solved by direct methods [triclinic, P1, a = 8.4784(6), b = 9.7873(8), c = 9.8121(7) Å, α = 90.170(2), β = 95.744(2), γ = 90.136(2)°, V = 810.12(10) Å3, Z = 1] and refined to R1 = 0.0146 (wR2 = 0.0336) for 5378 reflections with |F0| ≥ 4σF using least square techniques. The structures of 1 and 2 are based upon the [(UO2)2(TO4)3]2- (T = Se, S) twodimensional uranyl layers formed by linkage of U pentagonal bipyramids and TO4 tetrahedra via common O atoms. The layers consist of two types of 4-membered rings; this topology has previously been observed in the structures of several actinyl compounds that crystallize in tetragonal or orthorhombic space groups. Violation of the higher symmetry is caused by tiltings of the TO4 tetrahedra, associated with displacement of bridging oxygen atoms from their ideal position induced by the formation of moderate hydrogen bonds with the organic cations.

Supramolecular templates for the synthesis of new nanostructured uranyl compounds: Crystal structure of [NH3(CH2)9NH3][(UO2)(SeO4)(SeO2OH)](NO3)

AbstractCrystals of a new uranyl selenate, [NH3(CH2)9NH3][(UO2)(SeO4)(SeO2OH)](NO3) (1), were prepared by isothermal evaporation from aqueous solution at room temperature. The crystal structure was solved by the direct method