A new class of carbon 1D structures with symmetry of rod groups P61 and P31 – laterally-extended expanded nanohelicenes (NHs) with zigzag edge morphology – has been thoroughly investigated in the DFT framework. It is shown that these compounds can be divided into two groups, with each group having its distinct properties. The spiral ribbons of NHs of the first and second groups have odd and even numbers of carbon hexagons across, respectively. The first group members are semiconductors and their electronic band gap strongly depends on the uniaxial strain. Expanding the “shaft” (the inner hollow region in a NH spiral) results in a smooth decrease of the electronic band gap. If the outer edge of a NH includes fewer than seven hexagons, then the NH is diamagnetic. When the edge includes seven or more hexagons, antiferromagnetic ordering appears. The second group consists of NHs which are diamagnetic metals at equilibrium geometry that, however, undergo a phase transition to antiferromagnetic semiconductors under small (about 10%) elastic stretching. The difference between the electronic and magnetic properties of NHs in the first and second groups stems from the difference in their electronic structure and can be explained using group theory.

This paper presents synthesis and photophysical investigation of a very rare type of the ReI diimine complexes, [Re(diimine)(CO)3(OPR3)]+, R = Ph, Cy; diimine – phenanthroline and neocuproine, containing monodentate (unsupported) phosphine oxide ligands. The obtained compounds have been structurally characterized in solid phase by using XRD crystallography, which revealed unusual distortions in the pseudo octahedral rhenium environment, which may be ascribed to intramolecular interligand (phosphine oxide – diimine) interaction rather than to crystal packing effect. Optimization of the ground state structure of these molecules with the DFT method also confirmed intramolecular origin of the observed structural peculiarities. The complexes display phosphorescence in solution and in solid state with the quantum yield up to 11 % and 14 %, respectively, which originates from 3MLCT excited state as demonstrated by DFT calculations. Comparative analysis of the ligand (L) effect onto emission energy in the [Re(neocuproine)(CO)3(L)] complexes (L = PPh3, NCMe, OPPh3, Cl–) showed that the position of emission wavelength in the corresponding complexes qualitatively correlates with cumulative donor ability of these ligands that is in complete agreement with the 3MLCT character of emission.

Near-infrared (NIR) molecular emitters based on transition-metal complexes have attracted growing attention due to their potential application for in vivo and in vitro bioimaging experiments. Their photophysical characteristics (large Stokes shift and lifetime in the microsecond domain) offer some important advantages in comparison to organic fluorophores and may provide better imaging resolution and higher sensitivity: for example, in mapping the oxygen concentration in biological objects. We have synthesized a series of [Ir(N<^>C)(2)(N<^>N)](+) complexes with emission in the NIR region (N<^>C = (2-benzothienyl)-phenanthridine and 6-(2-benzothienyl)phenanthridine-2-carboxylic acid; N<^>N = functionalized pyridine-triazole chelates), which also display a considerable red shift of their excitation spectra to the window of transparency. The flexible protocol for the synthesis of the N<^>N ligands makes possible wide variations in the peripheral ligand environment: e.g., insertion of hydrophilic carboxyl group and further attachment of the other biologically relevant functions. The compounds obtained were completely characterized using spectroscopic methods, and their ground-state structures and photophysical properties were studied by DFT and TD DFT methods. To analyze the behavior of these emitters in biological systems, we investigated their interaction with human serum albumin (HSA), as the most abundant serum protein. It was found that these complexes readily form noncovalent {HSA-complex} adducts by embedding into hydrophobic cavities of this protein that also induced its partial aggregation. The complexes demonstrated preferential redistribution toward aggregated forms of HSA; the complex:HSA molar ratio did not exceed 1:3 for nonaggregated species. It was also shown that interaction of the hydrophobic complexes with albumin and the resulting aggregation dramatically change their important photophysical parameters such as emitter lifetime and its sensor response onto molecular oxygen.

Equilibrium oxygen isotope (O-18/O-16) fractionations (beta-factors) for corundum are predicted from first principles using the "frozen phonon" technique within the density functional theory (DFT). Calculations of the phonon frequencies and the isotopic frequency shifts were consequently performed over 1, 3, 8, and 27 wave vectors using the supercell approach, with the Gaussian-type all-electron basis sets and hybrid functional B3LYP. The presented phonon frequencies agree with experimental infra-red and Raman data. The results of beta-factor calculations are presented in terms of the logarithmic functions, 1000ln beta(crn), computed for temperatures from 0 to 2000 degrees C with a computational step of 20 degrees C and then fitted by the conventional cubic polynomial Ax + Bx(2) + Cx(3), with x = 10(6)/T(K)(2). The following expressions corrected for incomplete Brillouin-zone sampling quantify oxygen isotope fractionation of corundum. Within the harmonic approximation: 1000 ln beta(crn) = 9.2657x - 0.12110x(2) + 0.00175x(3) (0 < T degrees C < 2000).Accounting for thermal expansion (the quasi-harmonic approximation): 1000 ln beta(crn) = 9.03363x - 0.08912x(2) + 0.00036x(3) (0 < T degrees C < 1570 ) The pressure effect on corundum beta-factors is found to be negligible below ca. 25 kbar at temperatures exceeding 500 degrees C. At ultra-high pressures the correction can be made using the expression (partial derivative(1000ln beta)/partial derivative P)(T) (kbar) = 0.00967 x 10 (6)/T(K)(2).