Aromaticity of Roesky’s Ketone

The polythiazyl polymer (SN)x is an intrinsic electric polymeric conductor at room temperature and superconductor at temperatures close to absolute zero, having diverse applications in chemistry and chemical technology. In this work, electronic properties of the compounds with a (SN)2 unit enclosed in the ring stricture were examined. Namely, the aromaticity of Roesky’s ketone and its isomers was investigated by means of current density maps, multicentre delocalization indices (MCI) and nucleus-independent chemical shifts indices (NICS). The relative stability of the studied compounds was compared based on the calculated BLYP and CASSCF energies

How does aromaticity rule the thermodynamic stability of hydroporphyrins?

Several measures of aromaticity including energetic, magnetic, and electron density criteria are employed to show how aromatic stabilization can explain the stability sequence of hydroporphyrins, ranging from porphin to octahydroporphin, and their preferred hydrogenation paths. The methods employed involve topological resonance energies and their circuit energy effects, bond resonance energies, multicenter delocalization indices, ring current maps, magnetic susceptibilities, and nuclear-independent chemical shifts. To compare the information obtained by the different methods, the results have been put in the same scale by using recently proposed approaches. It is found that all of them provide essentially the same information and lead to similar conclusions. Also, hydrogenation energies along different hydrogenation paths connecting porphin with octahydroporphin have been calculated with density functional theory. It is shown by using the methods mentioned above that the relative stability of different hydroporphyrin isomers and the observed inaccessibility of octahydroporphin both synthetically and in nature can be perfectly rationalized in terms of aromaticity

Heterotrimetallic compounds containing Mo-M-Li [M = K, Rb and Cs] clusters : synthesis, structure, bonding, aromaticity and theoretical investigations of Li₂M₂ [M = K and Rb] and Cs₄ rings

A new polydentate fac-trioxo molybdenum complex, [MoO3L]3− {LH3 = nitrilotriacetic acid}, has been synthesized by the reaction of lithium molybdate with iminodiacetic acid. The trinegative complex anion coordinates the alkali metal cations, K+, Rb+ or Cs+. The potassium, rubidium and cesium complexes, [Li{K(H2O)2}MoO3L]n (1), [Li{Rb(H2O)2}MoO3L]n (2) and [Cs{Li(H2O)}2MoO3L]n (3), form heterotrimetallic coordination chains, containing planar rings of Li2M2 (M = K or Rb) and Cs4. Theoretical investigations on these rings were carried out using NICS calculations and ab initio ring current maps, revealing aromaticity to be of limited significance

Dependence of Hess-Schaad resonance energy on Kekulé structures

The Hess-Schaad resonance energy is defined as RE = E - Eref where E is the total π-electron energy and Eref is the reference energy computed by adding double- and single-bond contributions pertaining to some Kekulé structure. Therefore RE depends on the Kekulé structure considered. We show that in the case of benzenoid molecules the number of only one double-bond type determines RE. Furthermore, RE is a monotonically increasing function of the number of double bonds of type 3-3 or 2-2, and a monotonically decreasing function of the number of double bonds of type 2-3. This implies that RE is maximal if the respective Kekulé structure has the greatest possible number of double bonds of type 3-3, or the greatest possible number of double bonds of type 2-2, or the smallest possible number of double bonds of type 2-3.Publishe

Curcumin and diclofenac therapeutic efficacy enhancement applying transdermal hydrogel polymer films, based on carrageenan, alginate and poloxamer

Films based on carrageenan, alginate and poloxamer 407 have been formulated with the main aim to apply prepared formulations in wound healing process. The formulated films were loaded with diclofenac, an anti-inflammatory drug, as well as diclofenac and curcumin, as multipurpose drug, in order to enhance encapsulation and achieve controlled release of these low bioavailable compounds. The obtained data demonstrated improved drugs bioavailability (encapsulation efficiency higher than 90%), with achieved high, cumulative in vitro release percentages (90.10% for diclofenac; 89.85% for curcumin and 95.61% for diclofenac in mixture-incorporated films).. The results obtained using theoretical models suggested that curcumin establish stronger, primarily dispersion interactions with carrier, in comparison with diclofenac. Curcumin and diclofenac-loaded films showed a great antibacterial activity against Gram-positive bacteria strains (Bacillus subtilis and Staphylococcus aureus, inhibition zone 16.67 mm and 13.67 mm, respectively), and in vitro and in vivo studies indicated that curcumin- and diclofenac-incorporated polymer films have a great tendency, as a new transdermal dressing, to heal wounds, because diclofenac can target the inflammatory phase and reduce pain, whereas curcumin can enhance and promote wound healing process

Total π-electron energy and Laplacian energy: How far the analogy goes?

The Laplacian energy LE is a newly introduced molecular-graph-based analog of the total π-electron energy E. It is shown that LE and E have a similar structure-dependency only when molecules of different sizes are compared, when a good linear correlation between them exists. Within classes of isomers, LE and E are either not correlated at all or (as in the case of acyclic systems) are inversely proportional. The acyclic graphs and molecular graphs having the greatest and smallest LE values (determined in this work) differ significantly from those (previously known) having the greatest and smallest E values

Cyclic conjugation in benzo-annelated coronenes

The cyclic conjugation in benzo-annelated coronenes is studied by means of the energy effect (ef) and π-electron content (EC) of the six-membered rings. Some peculiarities of the π-electron structure of benzo-coronenes, inferred by the Clar aromatic sextet theory, could be tested and verified. A regularity that earlier was discovered in the case of perylene congeners is now shown to hold also for benzo-annelated coronenes: Benzenoid rings that are annelated linearly with regard to the central hexagon H0 of coronene decrease the intensity of cyclic conjugation in H0 and this effect is proportional to the number of linearly annelated rings. A very good linear correlation exists between the ef- and EC-values