Ivan V. Ananyev

Efficient assembly of mono- and bis(1,2,4-oxadiazol-3-yl)furoxan scaffolds via tandem reactions of furoxanylamidoximes

A general, facile, highly effective one-pot protocol for the synthesis of new types of heterocyclic systems incorporating mono- and bis(1,2,4-oxadiazol-3-yl)furoxan cores based on the tandem heterocyclization of furoxanylamidoximes with various aliphatic, aromatic, and heterocyclic carboxylic acid chlorides under very mild conditions (Cs2CO3, MeCN, 20 °C) has been developed. In addition, a solvent-free approach for the (1,2,4-oxadiazol-3-yl)furoxan synthesis by the reaction of furoxanylamidoximes with trimethyl orthoformate catalyzed by Sc(OTf)3 has been achieved. The advantages of step economy and scope make these reactions a powerful tool for assembling heterocyclic scaffolds of general chemistry and biomedical interest.

Design of hybrid heterocyclic systems with a furoxanylpyridine core via tandem hetero-Diels–Alder/retro-Diels–Alder reactions of (1,2,4-triazin-3-yl)furoxans

Two convenient, facile, regioselective and highly effective one-pot protocols for the synthesis of previously unknown hybrid heterocyclic systems with the furoxanylpyridine core based on the tandem inverse-electron-demand hetero-Diels–Alder/retro-Diels–Alder reactions of the tailor-made (1,2,4-triazin-3-yl)furoxans with 1-(pyrrolidino)cyclohexene and norbornadiene have been developed. The methods comprise [4 + 2] cycloaddition of enamine or norbornadiene to the 1,2,4-triazine ring of (1,2,4-triazin-3-yl)furoxans followed by one-pot transformation of the formed intermediates and this affords an extensive series of polyheterocyclic ensembles combining furoxan and pyridine (tetrahydroisoquinoline, indenopyridine, terpyridine) rings in one molecule through a C–C bond in good to excellent yields.

Highly Luminescent, Water‐Soluble Lanthanide Fluorobenzoates: Syntheses, Structures and Photophysics, Part I: Lanthanide Pentafluorobenzoates

Highly luminescent, photostable, and soluble lanthanide pentafluorobenzoates have been synthesized and thoroughly characterized, with a focus on Eu(III) and Tb(III) complexes as visible emitters and Nd(III) , Er(III) , and Yb(III) complexes as infrared emitters. Investigation of the crystal structures of the complexes in powder form and as single crystals by using X-ray diffraction revealed five different structural types, including monomeric, dimeric, and polymeric. The local structure in different solutions was studied by using X-ray absorption spectroscopy. The photoluminescence quantum yields (PLQYs) of terbium and europium complexes were 39 and 15 %, respectively; the latter value was increased almost twice by using the heterometallic complex [Tb0.5 Eu0.5 (pfb)3 (H2 O)] (Hpfb=pentafluorobenzoic acid). Due to the effectively utilized sensitization strategy (pfb)(-) →Tb→Eu, a pure europium luminescence with a PLQY of 29 % was achieved.

Toward a Rigorous Definition of a Strength of Any Interaction Between Bader’s Atomic Basins

Strength of interaction between Baders atomic basins, enclosed by zero-flux surfaces of electron distribution, was proposed to be a measure of elastic deformation of an interaction. The set containing 53 atomic aggregate and covering all range of interaction strength (from van der Waals interactions to triple covalent bonds) was calculated by DFT and perturbation theory methods. Further analysis was performed to seek correlations between various local quantities based on electron density and effective force constants of stretching diatomic vibrations. The linear trend between effective force constants and the potential energy density at the (3, -1) critical point of electron distribution was found. This correlation was improved by the integration of the potential energy density over an interbasin zero-flux surface of electron density. Simple mechanical explanation of established trends is presented. The correlations can be further used to at least semiquantitatively compare any pair of interactions between Baders atomic basins.

Tuning of the double-well potential of short strong hydrogen bonds by ionic interactions in alkali metal hydrodicarboxylates

Short strong hydrogen bonds within crystals of sodium and potassium hydrofumarates were investigated by means of high-resolution and multitemperature X-ray diffraction studies. Various parameters, including geometry data, displacement parameters and cation–anion interaction energy, are considered to discuss hydrogen atom disorder. The influence of cation–anion interactions, being mainly electrostatic in nature, on the H-bond peculiarities is discussed. Equations interlinking the distance and energy of metal-oxygen interactions are introduced for carboxylates of sodium and potassium.

Electrophilic–Nucleophilic Dualism of Nickel(II) toward Ni···I Noncovalent Interactions: Semicoordination of Iodine Centers via Electron Belt and Halogen Bonding via σ-Hole

The nitrosoguanidinate complex [Ni{NH═C(NMe2)NN(O)}2] (1) was cocrystallized with I2 and sym-trifluorotriiodobenzene (FIB) to give associates 1·2I2 and 1·2FIB. Structures of these solid species were studied by XRD followed by topological analysis of the electron density distribution within the framework of Baders approach (QTAIM) at the M06/DZP-DKH level of theory and Hirshfeld surface analysis. Our results along with inspection of XRD (CCDC) data, accompanied by the theoretical calculations, allowed the identification of three types of Ni···I contacts. The Ni···I semicoordination of the electrophilic nickel(II) center with electron belt of I2 was observed in 1·2I2, the metal-involving halogen bonding between the nucleophilic nickel(II)-dz2 center and σ-hole of iodine center was recognized and confirmed theoretically in the structure of [FeNi(CN)4(IPz)(H2O)]n (IPz = 4-N-coordinated 2-I-pyrazine), whereas the arrangement of FIB in 1·2FIB provides a boundary case between the semicoordination and the halogen Ni···I bondings. In 1·2I2 and 1·2FIB, noncovalent interactions were studied by variable temperature XRD detecting the expansion of noncovalent contacts with preservation of covalent bond lengths upon the temperature increase from 100 to 300 K. The nature and energies of all identified types of the Ni···I noncovalent interactions in the obtained (1·2I2 and 1·2FIB) and in the previously reported ([FeNi(CN)4(IPz)(H2O)]n, [NiL2](I3)2·2I2 (L = o-phenylene-bis(dimethylphosphine), [NiL]I2 (L = 1,4,8,11-tetra-azacyclotetradecane), Ni(en)2]n[AgI2]2n (en = ethylenediamine), and [NiL](ClO4) (L = 4-iodo-2-((2-(2-(2-pyridyl)ethylsulfanyl)ethylimino)methyl)-phenolate)) structures were studied theoretically. The estimated strengths of these Ni···I noncovalent contacts vary from 1.6 to 4.1 kcal/mol and, as expected, become weaker on heating. This work is the first emphasizing electrophilic-nucleophilic dualism of any metal center toward noncovalent interactions.

Conjugation effects in a para-nitroaniline molecule and its structural non-rigidity

A thorough investigation of the spatial and electronic structures of p-nitroaniline using the precision X-ray diffraction analysis and quantum chemical calculations in the framework of the “Atoms in Molecules” theory revealed that the conjugation of functional groups with the benzene ring is small and amino group flattening in crystal compared to the gas phase is caused by the inductive effects. The structure non-rigidity of the nitro group was observed, which appears as its dynamic disordering confirming that the conjugation with the benzene ring is energetically unfavorable compared to the intrinsic conjugation effects. In case of the amino group, only the static temperature-independent disorder as a superposition of two non-planar configurations can be proposed according to the results of normal coordinate analysis by the simulation of mean-square amplitude matrixes using multi-temperature X-ray diffraction data.

Vibrational smearing of the electron density as function of the strength and directionality of interatomic interactions: nonvalent interactions of a nitro group within an island-type crystal [Fe(NO)2(SC6H4NO2)]2

We consider the static and dynamic characteristics of interatomic bonding in the region of nonvalent interactions of a nitro group in the crystal of complex [Fe(NO)2(SC6H4NO2)]2. Based on results obtained by modeling vibrations within the framework of the density functional theory and those of multitemperature X-ray diffraction studies, a purely vibrational nature of the abnormally large atomic displacement ellipsoid of one of the O atoms of the nitro group was revealed and a model for the influence of peculiar features of intermolecular bonding on the observed dynamics was suggested. Using topological analysis of the experimental electron density function, we studied the nature of nonvalent intermolecular interactions of the nitro group and evaluated their strength and directionality in the equilibrium state. The dependence of the “pseudodegeneracy” region of atom—atom interaction on the nature of the interaction revealed and a method for determining the vibrational smearing of interactions was suggested, which allows one to analyze the stability of the connectivity graph of the crystal.

Features of chemical bonding within the Fe(NO)2 fragment for crystalline bis(thiosulfate) tetranitrosyl diiron tetramethylammonium salt as an example according to high-resolution X-ray diffraction data

Results of the study of the experimental charge density function for a crystal of the watersoluble {(СH3)4N+}2[Fe2(S2O3)2(NO)4] iron complex are presented. An inequality of two NO ligands at the same metal atom follows from the results of topological analysis of the charge density reconstructed particularly by using the “invariom” model. The inequality also reproduces that in the earlier studied complex Fe(SC2H3N3)(SC2H2N3)(NO)2]•0.5H2O, which is not caused by a superposition of spin states. Crystal packing analysis demonstrates the absence of a significant influence of solvation effects on the observed features of chemical bonding in the Fe(NO)2 fragment.

New 8-aryl-8´-iodo derivatives of cobalt bis(1,2-dicarbollide)

Reactions of 8,8´-μ-iodo-3-commo-3-cobalta[bis(1,2-dicarba-closo-dodecaborane)] (8,8´-μI-3,3´-Co(1,2-C2B9H10)2) with aryl halides (fluoro-, chloro-, bromo-, iodo-, and o-dichlorobenzenes) were studied. The reaction of 8,8´-μ-I-3,3´-Co(1,2-C2B9H10)2 with these reagents proceeded only in the presence of sterically hindered Lewis bases with the cleavage of the bridging B—I bond and the formation of the corresponding anionic 8-aryl-8´-iodo derivatives of cobalt bis(1,2-dicarbollide). X-ray diffraction studies were carried out for the charge-compensated 8´-iodo-8-(4,1-oxathian-1-ium)icosahydro-1,1´,2,2´-tetracarba-3-commo-cobaltacloso-tricosaborate and the anionic tetramethylpiperidinium 8´-(3,4-dichlorophenyl)-8-iodoicosahydro-1,1´,2,2´-tetracarba-3-commo-cobalta-closo-tricosaborate. The X-ray diffraction data showed that the molecule of the former compound has the gauche conformation, whereas the anionic complex is in the trans conformation.