The Laplacian energy LE is a newly introduced molecular-graph-based analog of the total ?-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.

In this paper, a detailed study of the local aromaticity in a series of cyclopenta-fused linear polyacenes (acenaphthylene derivatives) was performed using several different criteria of aromaticity. Namely, the energy effect (ef), bond resonance energy (BRE), harmonic oscillator model of aromaticity (HOMA) index, multi centre delocalization indices (MCI), electron density at ring critical points ρ(r_C), nucleus independent chemical shifts (NICS) and ring current maps were employed. All these methods agree that the extent of aromaticity of the five-membered ring in the acenaphthylene molecule is quite small. On the other hand, it was shown that the aromatic character of the five-membered rings depends on the size of the polyacenic part and on the position of the five-membered ring along the polyacenic part of the given acenaphthylene derivatives. According to energetic, electron delocalization and geometrical indices, the aromatic character of the pentagons in some higher acenaphthylene congeners is of the same order of magnitude as the aromatic character of some hexagons in the respective molecules. Ring current maps revealed the existence of a weak paratropic (antiaromatic) circulation in the five-membered rings which, in the case of higher members of the homolog series, becomes weaker. In contrast, the NICS indices showed a significant antiaromatic character of the five-membered rings in higher members of the acenaphthylene series.

Gold(III) complexes with 1,7- and 4,7-phenanthroline ligands, [AuCl3(1,7-phen-κN7)] (1) and [AuCl3(4,7-phen-κN4)] (2) were synthesized and structurally characterized by spectroscopic (NMR, IR and UV-vis) and single-crystal X-ray diffraction techniques. In these complexes, 1,7- and 4,7-phenanthrolines are monodentatedly coordinated to the Au(III) ion through the N7 and N4 nitrogen atoms, respectively. In comparison to the clinically relevant anti-angiogenic compounds auranofin and sunitinib, gold(III)-phenanthroline complexes showed from 1.5- to 20-fold higher anti-angiogenic potential, and 13- and 118-fold lower toxicity. Among the tested compounds, complex 1 was the most potent and may be an excellent anti-angiogenic drug candidate, since it showed strong anti-angiogenic activity in zebrafish embryos achieving IC50 value (concentration resulting in an anti-angiogenic phenotype at 50% of embryos) of 2.89μM, while had low toxicity with LC50 value (the concentration inducing the lethal effect of 50% embryos) of 128μM. Molecular docking study revealed that both complexes and ligands could suppress angiogenesis targeting the multiple major regulators of angiogenesis, such as the vascular endothelial growth factor receptor (VEGFR-2), the matrix metalloproteases (MMP-2 and MMP-9), and thioredoxin reductase (TrxR1), where the complexes showed higher binding affinity in comparison to ligands, and particularly to auranofin, but comparable to sunitinib, an anti-angiogenic drug of clinical relevance.

Aromatic character of nitrogen-containing rings is decreased upon gold( iii ) coordination.