Spin-Spin Artificial DNA Intercalated with Silver Cations: Theoretical Prediction

The Relativistic Effects on the Carbon-Carbon Coupling Constants Mediated by a Heavy Atom

The (2)JCC, (3)JCC, and (4)JCC spin-spin coupling constants in the systems with a heavy atom (Cd, In, Sn, Sb, Te, Hg, Tl, Pb, Bi, and Po) in the coupling path have been calculated by means of density functional theory. The main goal was to estimate the relativistic effects on spin-spin coupling constants and to explore the factors which may influence them, including the nature of the heavy atom and carbon hybridization. The methods applied range, in order of reduced complexity, from the Dirac-Kohn-Sham (DKS) method (density functional theory with four-component Dirac-Coulomb Hamiltonian), through DFT with two- and one-component zeroth-order regular approximation (ZORA) Hamiltonians, to scalar effective core potentials (ECPs) with the nonrelativistic Hamiltonian. The use of DKS and ZORA methods leads to very similar results, and small-core ECPs of the MDF and MWB variety reproduce correctly the scalar relativistic effects. Scalar relativistic effects usually are larger than the spin-orbit coupling effects. The latter tend to influence the most the coupling constants of the sp(3)-hybridized carbon atoms and in compounds of the p-block heavy atoms. Large spin-orbit coupling contributions for the Po compounds are probably connected with the inverse of the lowest triplet excitation energy.

Indirect relativistic bridge and substituent effects from the 'heavy' environment on the one-bond and two-bond (13)C-(1)H spin-spin coupling constants

Indirect relativistic bridge effect (IRBE) and indirect relativistic substituent effect (IRSE) induced by the 'heavy' environment of the IV-th, V-th and VI-th main group elements on the one-bond and geminal (13)C-(1)H spin-spin coupling constants are observed, and spin-orbit parts of these two effects were interpreted in terms of the third-order Rayleigh-Schrödinger perturbation theory. Both effects, IRBE and IRSE, rapidly increase with the total atomic charge of the substituents at the coupled carbon. The accumulation of IRSE for geminal coupling constants is not linear with respect to the number of substituents in contrast to the one-bond couplings where IRSE is an essentially additive quantity.

Structures, physicochemical properties, and applications of T–HgII–T, C–AgI–C, and other metallo-base-pairs

In this feature article, recent progress and future perspectives of metal-mediated base-pairs such as T–Hg(ii)–T and C–Ag(i)–C are presented.

What factors influence the metal-proton spin-spin coupling constants in mercury- and cadmium-substutited rubredoxin?

The indirect metal-proton spin-spin coupling constants between protons in cysteine groups and the mercury or cadmium nucleus have been calculated for a small model of Me-rubredoxin complex (Me = Cd, Hg) by means of density functional theory with zeroth-order regular approximation Hamiltonian (DFT-ZORA). The calculated spin-spin coupling constants, in spite of the moderate size of the model system, are in good agreement with the values measured in NMR experiment, which are in the 0.29-0.56 Hz range for the Cd complex and in the 0.57-2.20 Hz range for the Hg complex. The robustness of the chosen method has been verified by calculations with a number of different exchange-correlation functionals and basis sets. Additionally, it has been shown that the short- and long-distance metal-proton coupling constants are affected mainly by the values of the metal-proton distance and the H-N-C-C dihedral angle.