Ab initio electronic structure calculations and variational transition state theory are used to calculate reaction energetics and rate constants for the gas-phase reactions of OH- with CH(4 - n )Cl n for n = 1−4. Two reaction pathways are considered, second-order (bimolecular) nucleophilic substitution (SN2), and proton transfer. Benchmark electronic structure calculations using CCSD(T) and basis sets as large as aug-cc-pVQZ are performed to obtain highly accurate estimates of the enthalpies of reaction. These results are extrapolated to the complete basis set limit for comparison with experiment and to establish the level of theory needed to provide energies that are accurate to better than a few kJ/mol. Energies of critical geometries (reactant complexes, saddle points, and product complexes) are computed for all systems. For the SN2 reaction, the potential energy and its first and second derivatives along minimum energy paths are computed and used directly in variational transition state theory (VTST) calculations of the rate constants. These calculations indicate that for n = 1−3 the region of the potential in the asymptotic reactant channel controls the reaction rate constants and that the loose-transition-state methods implemented in variflex provide the best estimates of the reaction rate constants. The reaction with n = 4 has a dynamical bottleneck that lies near the saddle point and is best treated using the VTST methods implemented in polyrate.

Photochemical properties of a series of bifunctional monosubstituted derivatives of cymantrene containing a C-, N-, or O-bound π-allyl group, along with n-donating carbamate, amide, or pyridine fragments were investigated. The results obtained demonstrate that the nature and thermodynamic stability of the cyclopentadienylmanganese dicarbonyl chelates derived from bifunctional monosubstituted cymantrene derivatives depend substantially on both the nature of the functional groups and on their position in the substituent at the Cp ring. Thus, for the six-membered chelates, the thermodynamic stability increases in the series carbamates < amides < pyridines < olefins. Some of the dicarbonyl chelates studied form reversible photochromic systems due to linkage isomerization between different donating groups of the bifunctional substituent and the manganese atom with a wide range of times of thermal isomerization.

This study utilizes ab initio calculations to investigate the reaction of high-temperature solid-state catalytic isotope exchange (HSCIE) between amino acids and spillover tritium. The Hartree−Fock approximation and second-order Møller−Plesset perturbation theory in conjunction with 6-31G* and aug-cc-pVDZ basis sets were used to calculate potential energy surfaces for the interactions between CH4, alanine, hydroxyproline, and the H3O+ ion. Ab initio calculations were used to estimate the activation energies and structures of the transition states of these reactions. The hydrogen exchange reaction occurs by a synchronous mechanism, with a transition state that is characterized by pentacoordinated carbon. The proposed one-center mechanism is in good agreement with observed retention of configuration of the asymmetric carbon atoms in the HSCIE reaction with spillover tritium in experiments. The regioselectivity and stereoselectivity of hydrogen isotope exchange in amino acids with spillover tritium can be predicted on the basis of ab initio calculations of interaction of this compound with a model acidic center, taking the H3O+ ion as an example.

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Solid-state catalytic isotope exchange of hydrogen under the action of spillover hydrogen in organic compounds applied on a nonorganic carrier has been studied. The deuterium-labeled peptide [D]dalargin containing 14 deuterium atoms, [D]melatonin, and [D]histamine with the 72–92% substitution degree of all C–H bonds were prepared by this reaction. The activation energy of hydrogen isotope exchange with T2 and D2 in glycine and α-aminoisobutyric acid was obtained experimentally. It was shown that for the studied reaction the kinetic isotopic effect is 1.2–1.4 by the Hartree–Fock method, which is several times smaller than one in the liquid-phase reactions. Quantum chemical calculations of the isotope shift values in the electronic spectra of deuterium-labeled metal ion complexes were performed using the RB3LYP/LanL2DZ and CIS/LanL2DZ methods for calculation of the ground and the excited states. It was shown for deuterium-labeled histamine complexes [D12]Pd(him)2Cl2 and [D12]Cu(him)2Cl that the isotopic effect of UV spectra was 1600 and 1800 cal/mol, respectively. The measurement of isotopic shifts for electronic transitions potentially can be utilized as a new informative method for the investigation of complex formation. The deuterium-labeled compounds were shown to be useful as internal standards for quantitative mass spectroscopy (MS) analysis.

Sulfur-containing cymantrene derivatives having one or two organometallic moieties were studied by NMR, IR, UV/Vis spectroscopic methods and CVA under irradiation conditions. Photolysis of compounds 1-3 leads to the formation of rare 4membered chelates 4, 5 and 8. In the presence of external ligand (L), dissociation of the MnÀ S bond occurred to form new dicarbonyl complexes with the MnÀ L bond, which demonstrates the hemilabile character of the chelates obtained. The results were confirmed by DFT calculations. CVA method showed manganese oxidation potential value increased in the case of dicarbonyls (1313 mV for 4) as compared to that of tricarbonyls (1067 mV for 1).

The synthesis of four new 1,2,3‐triazole derivatives and seven 1,2,3‐triazolium salts that contain an organometallic group (i.e., cymantrenyl and ferrocenyl) at either the N‐1, N‐2, or N‐3 position was realized. The alkylation of organometallic and organic triazole derivatives was investigated, and as a result of these studies, it was found that the presence of a good leaving group at the heterocyclic nitrogen atom led to transalkylation and subsequent migration of the N‐1 substituent to the N‐2 position of the triazole moiety. The nucleophilicity of the counterion of the triazolium salt influenced the transalkylation and isomerization processes, which suggests that the elimination of the N‐substituent most likely occurs though a concerted mechanism with nucleophilic assistance from the counterion. Thus, a new approach to the synthesis of 2,4‐disubstituted 1,2,3‐triazoles has been developed.

Enantiomeric-enriched ferrocene-modified pyrazoles were synthesized via the reaction of the ferrocene alcohol, (S)-FcCH(OH)CH3 (Fc = ferrocenyl), with various pyrazoles in acidic conditions at room temperature within several minutes. X-ray structural data for racemic (R,S)-1N-(3,5-dimethyl pyrazolyl)ethyl ferrocene (1) and its (S)-enantiomer (S)-1 were determined. A series of racemic pyrazolylalkyl ferrocenes was separated into enantiomers by analytical HPLC on β- and γ-cyclodextrins (CD) chiral stationary phases. The quantum chemical calculations of interaction energies of β-CD were carried out for both (R)- and (S)-enantiomers. A high correlation between experimental HPLC data and calculated interaction energies values was obtained.