Splitting of the <Emphasis Type="Italic">d</Emphasis><Superscript><Emphasis Type="Italic">N</Emphasis></Superscript> atomic states in icosahedral 3<Emphasis Type="Italic">d</Emphasis> metal endofullerenes M@C<Subscript>60</Subscript>

Group-theoretical and quantum-chemical investigations of the spectrum of low-lying excited states have been performed by the ROHF and FCI-RAS (Full CI in Restricted Active Space) methods for 3d metal endofullerenes (MEFs) M@C₆₀ (M =Mn, Cr, and Fe) in different charged states. The major purpose of this study is quantum-chemical verification of the anomalous (“non-Bethe’s”) character of splitting of the d ^N atomic states in an electrostatic field with icosahedral symmetry, predicted previously within the theory of integral invariants theory. The interrelation between the integral invariants theory and the quantumchemical methods applied in this work is considered in detail. Our calculations suggest that the d ^N atomic states in the icosahedral field generated by fullerene C60 (I _h ) on a metal atom (ion) remain non-split for different charged states of the metal and C₆₀. Reasons for this phenomenon and other possible approaches to verification of the prediction are discussed. It is demonstrated that the d ^N states of the encapsulated metal are split in icosahedral 3d MEFs only under very strong compression of these structures.     

Structural,Electronic and Tunable Magnetic Properties of Transition Metal Doped Rh<Subscript>8</Subscript> Cluster from First Principles Calculation

The configurations, electronic and magnetic properties of the Rh₇M (M?=?3d, 4d transition metal) are systematically investigated within the framework of the generalized gradient approximation density-functional theory (DFT-GGA). The results indicated that the ground state structures of Rh₇M (M?=?3d) clusters prefer to a bicapped octahedron configuration, while the Rh₇M (M?=?4d) clusters present a different degree of geometry reconstruction relative to the perfect cubic structure of Rh₈ cluster. In most cases, the doped clusters show relatively higher stability, indicating that impurity atoms could stabilize the pure Rh₈ cluster; the Rh₇M (M?=?3d, 4d) have smaller frontier orbital energy gaps in comparison to the host. The magnetic moments of Rh₇M (M?=?3d, 4d) exhibit a tunable magnetism with range from 3μ_B to 13μ_B and the Fe atom doping enhances the magnetic moment of mixed cluster.     

Structure of valence band in cluster model for cytochrome-<Emphasis Type="Italic">c</Emphasis>-oxidase active centers

The electron structure of cluster model for active centers of cytochrome-c-oxidase has been calculated by DFT (PBE) method in 6-31G basis. The cluster model was constructed on the basis of experimental PDB-structure and included 1105 hemoprotein atoms. The valence band ceiling of cytochromeoxidase active centers is shown to be formed by the atoms of carbon and nitrogen from porphyrin ring of cytochrome heme a₃ and atoms of carbon and nitrogen from imidazol moieties of histidine connected with Cu atom in cytochrome a₃. D-orbitals of Cu and Fe atoms from heme a₃ and d-orbital of Fe atom from heme a contribute mainly to the orbital group. A conclusion is made that the catalytic activity of the structure is determined by these two types of orbitals. Cu d-orbitals of cytochrome a are substantially low in energy. It is suggested that Cu atoms of cytochrome a shift the chemical potential of d-orbitals belonging to the active center that results in their easier electron accepting and releasing. This can be a decisive factor in the electron transport process.     

Aromaticity of Bare Iridium Trimers and Ir3M0/+ and $$\rm{Ir}_3M_2^{+/3+}$$ (M = Li,Na, K,and Be,Ca) Bimetallic Clusters

The structural stabilities, bonding nature, electronic properties, and aromaticity of bare iridium trimers \(\rm{Ir}_3^{+/-}\) with different geometries and spin multiplicities are studied at the DFT/B3LYP level of theory. The ground state of the \(\rm{Ir}_3^{+}\) cation is found to be the ³A₂ (C_2v) triplet state and the ground state of the \(\rm{Ir}_3^{-}\) anion the ⁵A₂ (C_2v) quintet state. A detailed molecular orbital (MO) analysis indicates that the ground-state \(\rm{Ir}_3^{+}\) ion (C_2v, ³A₂) possesses double (σ and partial δ) aromaticity as well as the ground-state \(\rm{Ir}_3^{-}\) ion (C_2v, ⁵A₂). The multiple d-orbital aromaticity is responsible for the totally delocalized three-center metal-metal bond of the triangular Ir₃ framework. \(\rm{Ir}_3^{-}\) (C_2v, ¹A₁) structure motif is perfectly preserved in pyramidal Ir₃M^0/+ (C_s, ¹A′) and bipyramidal \(\rm{Ir}_3M_2^{+/3+}\) (C_2v, ¹A₁) (M = Li, Na, K and Be, Ca) bimetallic clusters which also possess the corresponding d-orbital aromatic characters.     

A Quantum Chemical Study of C<Subscript>60</Subscript>Cl<Subscript>30</Subscript>, C<Subscript>60</Subscript>(OH)<Subscript>30</Subscript> Molecules and Fe@C<Subscript>60</Subscript>(OH)<Subscript>30</Subscript> Endocomplex

(U)PBE0/cc-pVDZ method is used to study the structure of C₆₀Cl₃₀, C₆₀(OH)₃₀ molecules and Fe@C₆₀(OH)₃₀ endocomplex. The triplet state of the endocomplex is shown to be the lowest in energy among its four states corresponding to different spin multiplicities and positions of Fe nucleus within the fullerene cavity. This state is characterized by bonding between the iron atom and one of two benzenoid cycles of the carbon cage, six internuclear Fe–C distances (208 pm), and 1s²2s²2p⁶3s²3p⁶3d^7.24s^0.14p^0.3 electron configuration of iron with spin population of 2.36.     

First-Principles Calculations of Magnetism in Nanoscale Carbon Materials Confining Metal with <Emphasis Type="Italic">f</Emphasis> Valence Electrons

The f electrons in the unfilled shell of actinide and lanthanide display complex bonding behavior and the hybridized sp electrons in carbon could show spin polarization in finite nanostructures. Correspondingly, materials combining these two features exhibit abundant magnetic properties. In this paper, we outline our first-principles calculations on various nanoscale carbon materials confining U and Gd which are representative actinide and lanthanide, respectively. The complex interaction between f electrons and sp electrons make the induced magnetic property sensitive to metal specie and carbon confinement. Specially, (1) The magnetism could be suppressed by stronger adsorption with vacancy sites on graphene and adjusted by varying the valence state of some endohedral metallofullerenes (EMFs). (2) The magnetic coupling between metal and carbon structures could be promoted by large curvature when confinement site is carbon nanotubes and altered by the adatom defect on fullerene cages. (3) Untrivial magnetic property with large net spin and asymmetric spin distribution is obtained by confining U atom and Gd atom in one fullerene as a heteronuclear EMF. These results contribute to a systematic understanding of the magnetism in nanoscale carbon materials confining metal with f valence electrons.     

Resonant photoemission and absorption spectroscopy study of the Cu<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>TiSe<Subscript>2</Subscript> electronic structure

The Cu3p and Cu2p resonance photoelectron spectra of the valence bands and core levels as well as Ti and CuL _2,3 absorption spectra for monocrystals 1T-Cu _x TiSe₂ were studied. The valence spectra obtained at Cu3p and Cu2p resonance drastically differ from each other. For Cu 3p-3d resonance, there are several bands corresponding to different channels of excited state decay. Spectra of the valence bands at Cu 2p-3d resonance are virtually identical to the spectra of pure TiSe₂. As follows from the absorption spectra, titanium atoms have the oxidation state 4+, whereas copper atoms are close to the free ion state.     

Ab Initio Theoretical Studies on the Kinetics of Hydrogen Abstraction Type Reactions of Hydroxyl Radicals with CH<Subscript>3</Subscript>CCl<Subscript>2</Subscript>F and CH<Subscript>3</Subscript>CClF<Subscript>2</Subscript>

The hydrogen abstraction reactions from CH₃Cl₂F (R-141b) and CH₃CClF₂ (R-142b) by OH radicals are studied theoretically by semi-classical transition state theory. The stationary points for the reactions are located by using KMLYP density functional method along with 6-311++G(2d,2p) basis set and MP2 method along with 6-311+G(d,p) basis set. Single-point energy calculations are performed by the CBS-Q and G4 combination methods on the geometries optimized at the KMLYP/6-311++G(2d,2p) level of theory. Vibrational anharmonicity coefficients, x _ij , which are needed for semi-classical transition state theory calculations, are computed at the KMLYP/6-311++G(2d,2p) and MP2/6-311+G(d,p) levels of theory. The computed barrier heights are slightly sensitive to the quantum-chemical method. Thermal rate coefficients are computed over the temperature range from 200 to 2000 K and they are shown to be in accordance with available experimental data. On the basis of the computed rate coefficients, the tropospheric lifetime of the CH₃CCl₂F and CH₃CClF₂ are estimated to be about 6.5 and 12.0 years, respectively.     

Synthesis and sorption properties of layered hydrous manganese dioxide saturated with <Emphasis Type="Italic">s</Emphasis>-, <Emphasis Type="Italic">p</Emphasis>-, and <Emphasis Type="Italic">d</Emphasis>-metal cations

Layered compounds based on hydrous manganese dioxide (hereafter, Mn-phases) saturated with s-metal (Ba²⁺), p-metal (Pb²⁺), and d-metal (Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, and Cd²⁺) cations, analogues of manganese minerals of oceanic ferromanganese formations (vernadite, birnessite, buserite-I, and asbolan), were prepared at 4–6°C. All Mn-phases have poorly ordered structures. The sorption properties of phase compounds were studied in relation to alkali-metal (Na⁺ and K⁺) and other s-, p-, and d-metal cations. The exchange capacities of Mn-phases for alkali cations are very low, within 0.02–0.10 mg-equiv/g; for the other cations, the exchange capacities are 0.13–4.20 mg-equiv/g. The sorption of divalent metal cations depends on the phase and chemical composition of the Mn-phase.     

Bioactive compounds from <Emphasis Type="Italic">Smilax excelsa</Emphasis> L.

Phytochemical investigation of EtOAc extract of Smilax excelsa has led to isolation and structure elucidation of five compounds. The structures of these compounds are established by different spectroscopic techniques including 1D and 2D-NMR, HRMS and ECD spectroscopy. The compounds were: solanesol (1), violasterol A (2), trans-resveratrol (3), 5-O-caffeoylshikimic acid (4) and 6-O-caffeoyl-β-d-fructofuranosyl-(2-1)-α-d-glucopyranoside (5). The configuration of compound 2 was established by electronic circular dichroism (ECD) spectroscopy. Meanwhile the cytotoxicity and antibacterial activity of the compounds were evaluated by MTT and MIC assays. Compounds 1 and 2 showed promising inhibition on MCF-7 cell line with IC₅₀ of 161.6 and 190.0 µM, respectively. Also compounds 2 and 3 illustrated activity against Staphylococcus aureus with MIC values of 142.5 and 136.9 µM, respectively.     

Experimental and Theoretical Vibrational Spectra of Sideridiol Isolated from <Emphasis Type="Italic">Sideritis</Emphasis> Species

Sideridiol (ent-7α,18β-dihydroxykaur-15-ene) one of the ent-kaurene diterpenoid, is isolated from the genus Sideritis L. belongs to the family of Lamiaceae. The vibrational frequencies of sideridiol in the ground state have been calculated using the Density Functional Theory (DFT) method with the 6-31G(d) and 6 31+G(d,p) basis sets. The calculated vibrational frequencies have been compared with that of obtained experimental IR spectrum.     

Quantum-Chemical Study on Positional Selectivity in the Trimethylsilylation and Sulfonation of Pyrrole and <Emphasis Type="Italic">N</Emphasis>-Alkylpyrroles

Positional selectivity (α:β ratio) of electrophilic substitution in pyrrole, N-methylpyrrole, and N-tert-butylpyrrole was analyzed by ab initio [RHF/6-31G(d), MP2/6-31G(d)//RHF/6-31G(d)] and DFT [B3LYP/6-31G(d)] calculations of some σ-complexes derived from the substrates. The results of calculations with the use as model electrophilic species of trimethylsilyl cation [MP2/6-31G(d)//RHF/6-31G(d) and B3LYP/6-31G(d)] and SO₃ molecule [B3LYP/6-31G(d)] instead of proton are fairly consistent with the experimental data, according to which trimethylsilylation of pyrrole and its N-substituted derivatives with trimethylsilyl trifluoromethanesulfonate, as well as sulfonation with pyridine-sulfur trioxide complex, gives the corresponding β-substituted products.     

3<Emphasis Type="Italic">H</Emphasis>-Benzo[<Emphasis Type="Italic">a</Emphasis>]imidazo[4,5-<Emphasis Type="Italic">j</Emphasis>]acridine as a new fluorescent heterocyclic system: synthesis,spectral studies,and quantum chemical investigation

The synthesis, spectral studies, and theoretical calculations of a new fluorescent heterocyclic system are described. New 3H-benzo[a]imidazo[4,5-j]acridines were obtained in high yields by the reaction of 1-alkyl-5-nitro-1H-benzimidazoles with (naphthalen-1-yl)acetonitrile via nucleophilic substitution of hydrogen, and their structures were established by spectral (UV-Vis, FT-IR, 1H and 13C NMR) and analytical data. Study of the optical and solvatochromic properties of the dyes revealed their high molar absorption coefficients and high fluorescence quantum yields which in some cases exceeded quantum yields of well-known fluorescent dyes such as fluorescein. Density functional theory (DFT) calculations using the B3LYP hybrid functional and 6-311++G(d,p) basis set were performed to obtain optimized geometries and frontier orbital structures of the synthesized compounds. The electronic absorption spectra were also simulated by the time-dependent density functional theory (TD-DFT) method.     

Regioselectivity and regiospecificity of phosphorylation of (<Emphasis Type="Italic">Z</Emphasis>)- and (<Emphasis Type="Italic">E</Emphasis>)-4-chloromethylene-2-phenyl-5(4<Emphasis Type="Italic">H</Emphasis>)-oxazolones. Effect of solvation: Supramolecular approximation

By the methods of quantum chemistry in supramolecular approximation, are considered stereochemical and energetic features of phosphorylation of 4-chloromethylene-2-phenyl -5(4H)-oxazolone Z- and E-isomers in gas phase and their solvates with acetonitrile of 1:n composition where n varies from 1 to 10. On the MNDO-PM3 level the phosphorylation with triphenylphosphine proceeds endothermally in two steps: nucleophilic addition in the first step and elimination of chlorine anion with formation of phosphonium salt in the second step. Solvation with acetonitrile leads to stabilization of phosphonium intermediate and decrease in heat of conversion. On both semiempirical and nonempirical levels occur regioselectivity of nucleophilic attack at the double C=C, but not C=O, bond and regiospecificity of transformation without inversion of init configuration of the isomers owing to steric hindrances restricting rotation degree of freedom of -CHClP⁺Ph₃ group. Therewith, elimination of chlorine anion is characterized by low activation barrier and occurs with donation negative charge from π-orbital of carbon atom in the 4 position of heterocycle on antibonding σ*-orbital of carbon-chlorine bond; two orbitals become practically coplanar in the transition state.     

Synthesis and X-ray investigation of Rb<Subscript>2</Subscript>[Pd(NO<Subscript>3</Subscript>)<Subscript>4</Subscript>] and Cs<Subscript>2</Subscript>[Pd(NO<Subscript>3</Subscript>)<Subscript>4</Subscript>]

Powder and single crystal X-ray diffraction studies have been performed for anhydrous nitrate complexes Rb₂[Pd(NO₃)₄] (I) and Cs₂[Pd(NO₃)₄] (II). Crystal data for I: a = 7.843(1) Å, b = 7.970(1) Å, c = 9.725(1) Å; β = 100.39(1)°, V = 597.9(1) Å ³, space group P2₁/c, Z = 2, d _calc = 2.918 g/cm³; for II: a = 10.309(2) Å, b = 10.426(2) Å, c = 11.839(2) Å; β = 108.17(3)°, V = 1209.0(4) ų, space group P2₁/c, Z = 4, d ^calc = 3.408 g/cm³. The structures are formed by isolated [Pd(NO₃)₄]^2? complex anions and alkali metal cations. The plane-square environment of the Pd atom is formed from the oxygen atoms of the monodentate nitrate groups. The geometrical characteristics of the complex anions are analyzed. Compound II has a short contact Pd...Cs 3.252 Å.     

Synthesis and in vitro antibacterial evaluation of 6-substituted 4-amino-pyrazolo[3,4-<Emphasis Type="Italic">d</Emphasis>]pyrimidines

Pyrazolo[3,4-d]pyrimidines are one of the most important classes of fused heterocyclic compounds which exhibit a broad range of biological and medicinal properties. They are known as anticancer, antifungal, antibacterial, antiviral and anti-inflammatory agents. In this study, some new 6-substituted 4-amino-pyrazolo[3,4-d]pyrimidine derivatives were prepared via reaction of 5-amino-3-methyl-1-phenyl-1H-pyrazole-4-carbonitrile with various nitriles in the presence of sodium ethoxide as catalyst. The inhibitory properties of synthesized compounds were studied according to CLSI guidelines against some pathogenic bacteria including four gram-positive strains (Streptococcus pyogenes, Staphylococcus aureus, Bacillus cereus and Bacillus subtilis subsp. spizizenii) and three gram-negative strains (Pseudomonas aeruginosa, Shigella flexneri and Salmonella enterica subsp. enterica). The antibacterial effects of all derivatives were compared with those of antibiotics belonging to different classes. The values were reported as inhibition zone diameter (IZD), minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The effect of substituents on the biological activity of derivatives was discussed as well. The inhibitory effect of compound 6a, was shown to be the most, with MIC values in the range of 32–4096 μg/mL. Since most of the synthesized compounds were effective against Streptococcus pyogenes and Pseudomonas aeruginosa, they can be considered as inhibitors of these two bacteria.     

Crystal structures of <Emphasis Type="Italic">trans</Emphasis>-[Re<Subscript>6</Subscript>S<Subscript>8</Subscript>(CN)<Subscript>2</Subscript>L<Subscript>4</Subscript>] complexes,L = pyridine or 4-methylpyridine

The structures of three novel octahedral rhenium cluster compounds [Re₆S₈(CN)₂(py)₄]·H₂O (1), [Re₆S₈(CN)₂(4-Mepy)₄] (2), [Re₆S₈(CN)₂(4-Mepy)₄]·4-Mepy (3) (py = pyridine, 4-Mepy = 4-methylpyridine) are determined by X-ray crystallography. Crystal data are: C2/m space group, a = 14.813(1) Å, b = 14.772(1) Å, c = 9.2122(6) Å, β = 119.085(2)°, V = 1761.7(2) ų, d _x = 3.318 g/cm³, R = 0.0585 (1); I4₁/amd space group, a = 16.0018(3) Å, c = 14.7186(5) Å, V = 3768.81(16) ų, d _x = 3.169 g/cm³, R = 0.0489 (2); P2₁/c space group, a = 9.0452(4) Å, b = 15.8065(7) Å, c = 15.2951(6) Å, β = 103.700(2)°, V = 2124.57(16) ų, d _x = 2.957 g/cm³, R = 0.0245 (3). Molecular cluster complexes interact via π-π stacking affording 3D frameworks in 1 and 2 and chains in 3.     

The relation between the potential of zero charge and work function for <Emphasis Type="Italic">sp</Emphasis>-metals

It is shown that for numerous sp-metals there exists no unified work function (W _e) dependence of the potential of zero charge E _{q = 0} and the potential drop characterizing the metal lyophilic behavior Δ _M ^Hg E _chem) _{q = 0}. The reason is that the metal work function is by no means the only factor affecting the value of E _{q = 0}. The quantities E _{q = 0} and (Δ _M ^Hg E _chem) _{q = 0} depend also on the distance of the solvent dipoles’ closest approach to metal surfaces (d _ms) in the absence of the metal-solvent chemisorption interaction. When the metal-solvent chemisorption interaction is involved, this distance affects the degree of overlapping of the metal’s acceptor levels and the upper occupied donor levels in the solvent molecules. To reliably investigate the effect of any of these factors on E _{q = 0}, the other one should be fixed up. It is shown, by example of Ga-, Bi-Gaand Sn-Ga-electrodes, as well as Pb-Ga-, In-Ga-, and Cd-Ga-electrodes demonstrating very close values of the “electrochemical work function” that the metal-solvent chemisorption interaction becomes stronger with the decreasing of d _ms. The influence of this factor is intensified with the increasing of the solvent’s donor number DN. The W _e dependence of E _{q = 0} and (Δ _M ^Hg E _chem) _{q = 0} can be traced by example of metals with nearly equal d _ms values, e.g., Tl-Ga, In-Ga, and Ga. In all studied solvents, the deviation of E _{q = 0} from W _e increased in the series Tl-Ga < In-Ga < Ga, that is, with the increasing of the metal’s work function in vacuum. The effect is intensified with the increasing of the solvent’s DN. The obtained results agree with the concept of donor-acceptor nature of the metal-solvent chemisorption interaction.     

Sensitizing activity of metal tetraphenylporphines toward diethylaminobenzaldehyde <Emphasis Type="Italic">N,N</Emphasis>-diphenylhydrazone and its dependence on the central metal atom

The sensitizing activity of metal (Cu, Co, Ni, Zn, and Ag) tetraphenylporhines (TPPs) toward N,N-diphenylhydrazone of diethylaminobenzaldehyde was studied. It was found that the sensitized photosensitivity essentially depends on the electronic structure of the central metal atom in the TPP molecule: porphyrin complexes with metals that have vacant d or f shells or unpaired electrons (Co, Cu, Ni, and Ag TPPs) do not act as spectral sensitizers for diethylaminobenzaldehyde N,N-diphenylhydrazone.     

Modification of silica nanoparticles with stereisomers of <Emphasis Type="Italic">p</Emphasis>-<Emphasis Type="Italic">tert</Emphasis>-butylthiacalix[4]arene containing four 2-oxo-2-{[3-(triethoxysilyl)prop-1-yl]amino}ethoxy substituents at the lower rim

Three stereoisomers (cone, partial cone, and 1,3-alternate) of p-tert-butylthiacalix[4]arene bearing four anchor propyltriethoxysilane substituents at the lower rim were synthesized for the first time. Surface modification of silica nanoparticles (d = 12 nm) with the synthesized macrocycles gave novel hybride thiacalix [4]arene?SiO₂ particles. The obtained nanostructured adsorbents were found to efficiently extract nitroaromatic compounds from aqueous solutions. The partial cone and 1,3-alternate thiacalix[4]arene–SiO₂ hybrid particles showed affinity to nitrophenols.