Quantum-chemical modeling of endohedral derivatives of buckminsterfullerenes Gd@C<Subscript>60</Subscript>(CHR)<Subscript>2</Subscript> and Gd@C<Subscript>80</Subscript>(CHR)<Subscript>2</Subscript>

The structural energies of the endohedral derivatives of buckminsterfullerenes Gd@C₆₀(CHR)₂ and Gd@C₈₀(CHR)₂ were calculated by quantum-chemical methods – semiempirical PM3 and nonempirical RHF SCF MO LCAO with the S. Huzinaga MINI minimum basis set and GAMESS software.     

Mixed-ligand lanthanide complexes with acylpyrazolones and phosphorus-containing ligands

The reactions of lanthanum acetylacetonate with various phosphorus-containing pesticides, toxic gases, and products of their hydrolysis are modeled by quantum-chemical methods. In the most cases, the enthalpy of substitution for water by organophosphorus compounds is negative. The complexes are studied in solutions using ethyl (diethoxyphosphoryl) acetate as a model compound. The mixed-ligand lanthanide complexes with acylpyrazolones and ethyl (diethoxyphosphoryl) acetate are synthesized. The crystal structure is determined for the samarium complex.     

Solid-state NMR of endohedral hydrogen-fullerene complexes

We present an overview of solid-state NMR studies of endohedral H(2)-fullerene complexes, including (1)H and (13)C NMR spectra, (1)H and (13)C spin relaxation studies, and the results of (1)H dipole-dipole recoupling experiments. The available data involves three different endohedral H(2)-fullerene complexes, studied over a wide range of temperatures and applied magnetic fields. The symmetry of the cage influences strongly the motionally-averaged nuclear spin interactions of the endohedral H(2) species, as well as its spin relaxation behaviour. In addition, the non-bonding interactions between fullerene cages are influenced by the presence of endohedral hydrogen molecules. The review also presents several pieces of experimental data which are not yet understood, one example being the structured (1)H NMR lineshapes of endohedral H(2) molecules trapped in highly symmetric cages at cryogenic temperatures. This review demonstrates the richness of NMR phenomena displayed by H(2)-fullerene complexes, especially in the cryogenic regime.     

Tautomerism of metal complexes with 1,8-dihydroxy-3-R1-6-R2-9,10-anthraquinones

The structures of metal complexes with 1,8-dihydroxyanthraquinones studied by spectrophotometric, quantum-chemical, and correlation methods were found to be determined by tautomeric 9,10–1,10-anthraquinoid structures of the ligands and by the degree of the ligand ionization. Complex formation is accompanied by the shifts in tautomeric equilibria influencing both excited and ground states of the ligands. The 1,10-anthraquinoid forms of complexes are the most characteristic. The known complexes are classified in accordance with the ligand structures.     

Experimental and quantum-chemical studies of the reactions of 6-methyluracil with succinic and fumaric acids

Possible structures of 6-methyluracil complexes with succinic and fumaric acids are studied by quantum-chemical means. The possibility of complex formation occurring between 6-methyluracil and the acids in the ionized and nonionized states is evaluated. The form of the complexes containing the nonionized acid is found to dominate. The quantum-chemical calculation data are consistent with the experimental results.     

新型内嵌混合金属氮化物原子簇富勒烯的合成、结构与性质*

内嵌混合金属氮化物原子簇富勒烯的发现极大地扩展了内嵌富勒烯家族。内嵌混合金属氮化物原子簇富勒烯是一类新型的内嵌富勒烯,其内嵌物为由2-3种不同的金属组成的氮化物原子簇。本文首先介绍了新型内嵌混合金属氮化物原子簇富勒烯的发现、合成和分离方法,并对目前所分离出来的内嵌混合金属氮化物原子簇富勒烯进行了分类。然后总结了目前所报导的内嵌混合金属氮化物原子簇富勒烯的结构表征手段,对于不同的内嵌混合金属氮化物原子簇富勒烯的分子结构分别进行了阐述。最后着重讨论了内嵌混合金属氮化物原子簇富勒烯的特殊电子性质以及物理和化学性质。本文还对内嵌混合金属氮化物原子簇富勒烯潜在的应用前景作了展望,在内嵌具有不同物理性质的两到三种金属原子的基础上,所形成的内嵌混合金属氮化物原子簇富勒烯有可能兼具不同金属原子各自的性质,从而成为多功能综合的功能材料。     

B32及其包心化合物的电子结构与电子光谱的理论预测

在ＩＮＤＯ／ＣＩ方法的基础上，预测Ｂ３２及其包心化合物的电子结构与光谱，并与其共轭多面体Ｃ４０及其包心化合物进行对比。     

Investigating inclusion complexes using quantum chemical methods

Quantum chemistry has firmly established itself as a reliable method for investigating present-day problems in biological and materials chemistry. Understanding inclusion complexes represents one of the cutting edges of simulation sciences. In this tutorial review, we focus on the role and composition of non-covalent interactions, which are essential when studying inclusion complexes. A selected set of recently developed pragmatic methods used to study inclusion complexes are then surveyed including e.g. dispersion corrected DFT, double-hybrid functionals and spin-component scaled MP2. Finally, three case studies are outlined: (a) endohedral fullerene complexes, (b) buckyball catcher and (c) resorcinarene capsule. These case studies were carefully chosen to help illustrate how one may accurately investigate inclusion complexes, at a modest computational cost, using state-of-the-art quantum chemical methods (67 references).     

Donor-acceptor complexes of linear oligopyrroles with boron trifluoride. Spectral studies and quantum-chemical simulation

Intermediate products of synthesis of the boron trifluoride complexes with linear oligopyrroles are found. By means of electronic spectroscopy it was shown that the reaction of linear oligopyrroles with boron trifluoride in solutions resulted in the formation of stable donor-acceptor complexes. Their composition was established and the formation constants were evaluated. It was shown that transformation of these complexes in the corresponding borofluoride complexes is possible only while boiling the reaction mixture. By means of quantum-chemical methods the structural and energy parameters of the donor-acceptor complexes under study were calculated.     

C~4~0, C~4~0^+, Nb@C~4~0^+, NbC~3~9^+, Nb@C~4~0H~4^+的 量子化学研究

用量子化学从头计算方法研究了C~4~0,C~4~0^+,Nb@C~4~0^+,NbC~3~9^+,Nb@C~4~0H~4^+的几何构型、电子结构和C~2~8一样,C~4~0(T~d)基态也为^5A~2态,笼骨架上具有四个悬挂键。计算结果表明C~4~0和C~4~0^+比NbC~3~9^+和Nb@C~4~0^+稳定,与实验结果一致。     

Synthesis and properties of metal-ligand complexes with endohedral amine functionality

A series of tetracationic M(2)L(4) palladium-pyridyl complexes with endohedral amine functionality have been synthesized. The complexes were analyzed by NMR techniques (including Diffusion NMR and 2D NOESY), electrospray ionization (ESI) mass spectrometry, and X-ray crystallography. The solid state analysis shows a large change in crystal morphology upon introduction of the endohedral amine groups, caused by deleterious interactions between the amines and the triflate counterions from the coordination process. Combination of different ligands allows analysis of ligand exchange rates via NMR analysis, with half-lives on the order of 3 h, independent of the donor properties of the ligand. Self-sorting behavior is observed, with more electron-rich ligands being favored. The amine-containing and extended complexes are strongly fluorescent, giving quantum yields of up to 83%.     

富勒烯金属有机配合物的研究进展

介绍了近几年来富勒烯金属包合物、富勒烯球体与金属键联形成的配合物、富勒烯有机衍生物与金属原子形成的配合物以及富勒烯-有机金属配合物形成的共晶的研究进展.     

Sequential isomerism of activated complexes: Interfering versus noninterfering intermediate

A unimolecular process is considered that was treated experimentally as a concerted one; however, subsequent quantum-chemical analysis has proved that the process is realized via an intermediate (double sequential isomerism of activated complexes). The intermediate is supposed to contribute directly to values of the primary observed data (e.g., spectral absorbances). Within this approach of interfering intermediate any degree of this interference is allowed including the limit case of noninterfering intermediate serving as a reference standard. A technique is suggested enabling correct comparison of the quantum-chemical outputs with the experimental overall values for rate constants and activation enthalpy and entropy. The technique employs mere amount of information currently obtainable from quantum-chemical study of a rate process (i.e., representation of potential energy hypersurface by its stationary points and activated-complex theory). Properties of the derived formulae are illustrated with model examples. The results are important for meaningful comparison of experimental and theoretical data in the case of processes with sequential isomerism of activated complexes disclosed only theoretically.     

Metal Complexes with 1,5- and 1,8-Dihydroxy-9,10-Anthraquinones: Electronic Absorption Spectra and Structure of Ligands

Metal complexes with 1,5-dihydroxy-9,10-anthraquinone are studied by the spectrophotometric, quantum-chemical, and correlation methods. It was established that the ligand in these complexes can occur in seven excited states that differ not only in the ionization degree but also in the prevailing contribution of the tautomeric 9,10-, 1,10-, and 1,5-anthraquinoid structures. In all known complexes with 1,8-dihydroxy-9,10-anthraquinone and singly ionized ligand, this ligand has the 1,10-anthraquinoid structure; in complexes with the doubly ionized ligand, the latter ligand most often has the 9,10-anthraquinoid structure. The known complexes are classified according to the ligand structures.     

Kinetic resistance of borofluoride complexes of dipyrrolylmethenes to acids

The trends of kinetic resistance of borofluoride complexes of alkyl- and sulfo-substituted dipyrrolylmethene (Bodipy) to protolytic and solvoprotolytic dissociation in organic solvents and aqueous solutions are studied. It is established that among dipyrrolylmethene complexes with d elements, Bodipy is notable for its superresistance to acids. The rate of the dissociation reaction increases with increasing acidity of protonating mixtures or decreasing effective charge of the coordinating nitrogen atoms of the ligand. Dissociation of the complexes occurs in accordance with a second-order rate equation. A kinetic model of the process is proposed; its kinetic and activation parameters are determined. The energy profiles of the initial stages of protolytic dissociation reactions are calculated using quantum-chemical methods for two suggested variants of the transient state; the energetically preferable pathway is recognized.     

Open-cage fullerene derivatives suitable for the encapsulation of a hydrogen molecule

The encapsulation of molecular hydrogen into an open-cage fullerene having a 16-membered ring orifice has been investigated. It is achieved by the pressurization of H2 at 0.6-13.5 MPa to afford endohedral hydrogen complexes of open-cage fullerenes in up to 83% yield. The efficiency of encapsulation is dominantly dependent on both H2 pressure and temperature. Hydrogen molecules inside the C60 cage are observed in the range of -7.3 to -7.5 ppm in 1H NMR spectra, and the formations of hydrogen complexes are further confirmed by mass spectrometry. The trapped hydrogen is released by heating. The activation energy barriers for this process are determined to be 22-24 kcal/mol. The DSC measurement of the endohedral H2 complex reveals that the escape of H2 from the C60 cage corresponds to an exothermic process, indicating that encapsulated H2 destabilizes the fullerene.     

Complex formation in Cu(II)-thioamide-carbonyl compound systems in ethanol solutions

The structures of metal complexes formed in systems Cu(II)-thioamide-carbonyl compounds in water-ethanol solutions were studied by spectroscopic and quantum-chemical methods. It was found that in systems containing thiocarbohydrazide, the processes of template synthesis in water-ethanol solution and in gelatin-immobilized matrices differ substantially. In the case of dithiooxamide and dithiomalonamide, no products of template synthesis were detected; these amides give with the Cu²⁺ ion the chelate complexes with a ratio Cu²⁺: ligand = 1: 2 and with the N₂S₂ coordination core for dithiooxamide and S₄ coordination core for dithiomalonamide. The quantum-chemical calculations in terms of the density functional theory were shown to adequately describe the structures of metal complexes and relative thermodynamic characteristics of the template synthesis processes in the systems under study.     

Quantum-chemical study of thermodynamics of hydrogen-bonded methylamine-methanol complexes reaction with dimethyl carbonate

Thermodynamic parameters of the reactions of dimethyl carbonate cis-cis and cis-trans conformers with methylamine, methylamine dimer, and methylamine complexes involving linear methanol associates have been computed with the B3LYP and WB97XD quantum-chemical methods. The both methods have given similar results. Thermodynamically, reactions of the cis-trans conformer are preferred over the analogous reactions of the cis-cis conformer, and the reactions with methylamine dimer and methylamine-methanol trimer complex are preferred over the reactions with methylamine monomer. The acid-base properties of the hydrogen-bonded methanol complexes are significantly enhanced with increasing degree of association. Stability of the methylamine complexes with methanol clusters is increased with more of the alcohol molecules involved.     

Interaction of Siberian larch arabinogalactan with amino-containing compounds

The interaction of the natural polysaccharide arabinogalactan and its oxidized fractions with 5-aminosalicylic acid, 4-aminosalicylic acid, and isonicotinic acid hydrazide in aqueous solutions is investigated with the use of physicochemical methods. The compositions and stability constants of the formed complexes are studied, and the optimal conditions of their preparation are found. On the basis of spectral investigations and quantum-chemical calculations, the scheme of interaction between system components that leads to formation of cyclic structures is developed.     

Heating a bowl of single-molecule-soup: structure and desorption energetics of water-encapsulated open-cage [60] fullerenoid anions in the gas-phase

The gas-phase unimolecular decay kinetics of an anionic, open-cage [60] fullerene derivative encapsulating one water molecule is studied by means of black-body IR radiation induced dissociation (BIRD) in the temperature programmable ion trap of a Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometer. The primary reaction channel observed is escape of the water molecule from the fullerenoid bowl. The rate constants for this water loss as a function of temperature are evaluated using the Arrhenius equation to yield an activation energy of 104 ± 4 kJ mol(-1). A complementary ion mobility spectrometry study contrasting the water-encapsulated and the empty fullerene cages finds identical collision cross sections to within experimental error-supporting the structural assignment of this gas-phase anion as an endohedral (i.e. encapsulated) species. Both experiments were compared with quantum-chemical computations which well-describe the transition state for water desorption and the concomitant binding and activation energies.