Search results for "Heteroatom"

Tuning the electronic properties and the planarity degree in the π-extended TTF series: the prominent role of heteroatoms

2018

The main asset of small molecules for application in organic electronics lies in the tunability of their electronic properties owing to the precise control of their molecular design. Semiconducting properties in organic compounds are for instance closely linked to the molecular planarity degree, including when considering various redox states. Among those species, the π-extended TTF (exTTF: 9,10-bis(1,3-dithiol-2-ylidene)-9,10-dihydroanthracene) presents fascinating redox and structural properties, which have been extensively studied in various fields of organic electronics. Here we show that S-exTTF, a sulfur enriched π-isoelectronic dithieno analogue of pristine exTTF, synthesized through…

Impacts of Copper Position on the Electronic Structure of [Au25-xCux(SH)18]− Nanoclusters

2015

Here, we use density functional theory to model the impact of heteroatom position on the optoelectronic properties of mixed metal nanoclusters. First, we consider the well-described [Au25(SH)18]− motif, and substitute Cu atoms at the three geometrically unique positions within the cluster. These clusters are atomically precise and show an electronic structure that is a function of both composition and heteroatom position. We then model clusters containing Cu substitutions at two positions, and demonstrate an additional and significant impact from heteroatom proximity with respect to one another. For each system, we report the formation energy, HOMO–LUMO gap, and energy level structure, and …

Photoassisted Mineralization of Aromatic and Aliphatic N Heterocycles in Aqueous Titanium Dioxide Suspensions and the Fate of the Nitrogen Heteroatoms

2008

Abstract The photoassisted degradation of aromatic heterocycles (pyrrole, imidazole, pyrazole, isoxazole, oxazole and thiazole) and N-containing alicycles (aliphatic heterocycles: pyrrolidine, 4-butanelactam and 5-pentanelactam) was examined in liquid–solid dispersions. Complete mineralization (TOC) of the aromatic heterocycles was attained within ca. 1 h of UV irradiation of the TiO 2 /heterocycle system in acidic (pH 3), near-neutral (pH 6.0–7.6) and alkaline (pH 11) media. Mineralization kinetics were, in general, not appreciably influenced by the presence of acid but tended to be somewhat slower in alkaline media. N-alicycles were photomineralized more slowly than were the aromatics. Th…

Valence Topological Charge-Transfer Indices for Dipole Moments

2003

Valence topological charge-transfer (CT) indices are applied to the calculation of dipole moments. The dipole moments calculated by algebraic and vector semisums of the CT indices are defined. The combination of the CT indices allows the estimation of the dipole moments. The model is generalized for molecules with heteroatoms. The ability of the indices for the description of the molecular charge distribution is established by comparing them with the dipole moment of the valence-isoelectronic series of benzene and styrene. Two CT indices, μ v e c (vector semisum of vertex-pair dipole moments) and μ V v e c (valence μ v e c ) are proposed. μ v e c and μ V v e c are important for the predicti…

Eight-membered Rings with Two Heteroatoms 1,2

2008

This chapter deals with heterocine rings with two heteroatoms in a 1,2-relationship, namely 1,2-diazocine, 2H-1,2-oxazocine, 2H-1,2-thiazocine, 1,2-dioxocin, 1,2-oxathiocin, and 1,2-dithiocin. This chapter covers the literature from 1996 to 2006 and also reports those articles published in 1995 which were not reported in CHEC-II(1996). In this edition, in addition to the uncondensed derivatives, eight-membered 1,2-heterocycles fused to five-, six-, and seven-membered carbocycles or heterocycles are covered, although in one case a four-membered fused cycle was occasionally reported. Bridged heterocines, which actually constitute the majority of the compounds reported, are covered as well. Th…

The effect of trivalent framework heteroatoms in Cu-CHA on the Selective Catalytic Reduction of NO

2021

Abstract The effect of the trivalent framework atoms (Si4+/M3+ = 13-105) in Cu exchanged CHA-type zeolites was investigated for the selective catalytic reduction of NO with NH3. While the increased hydrophobicity of B-CHA compared to Al-CHA could make it a good candidate for low temperature SCR, the material was too unstable under reaction conditions and the exchanged Cu2+ did not remain isolated. Consequently a lower activity and selectivity than for Al-CHA were observed. Ga-CHA on the other hand showed a similar Cu2+ speciation as Al-CHA at similar Si4+/M3+ ratios. The difference in catalytic activity was remarkably small. While Ga-CHA was less stable upon hydrothermal aging, this was mar…

Unexplored analytics of some novel 3d–4f heterometallic Schiff base complexes

2014

Three heterometallic Schiff-base complexes of Cu having Pr, Nd and Sm as the heteroatoms have been synthesized. The compounds have also been characterized by their IR spectra and CHN analysis. The single crystal structures of these compounds have been studied from the X-ray crystallographic data. To the best of our knowledge the article describes the possibility of application of these compounds in the field of species dependent anion sensing for the first time. Amongst a number of anionic species, certain sulphur species were found to have greater reactivity towards a Schiff-base complex as they can incur probable changes in the molecular complexity. The S2O82−and S2O32− species could modi…

Thiophene series. Substituent effect on thiophenoxy debromination of various 2-nitro-3-bromo-5-X-thiophenes

1970

The kinetics of the reaction of a series of 2-nitro-3-bromo-5-X-thiophenes with sodium thiophenoxide in methanol were determined. The plot of log k against σ-values gave ρ-value + 4.51 at 20°. Good correlation was observed pointing out the validity of the Hammett relationship for reactions occurring directly on the thiophene ring at the β-position with respect to the heteroatom.

Hydration/elimination reactions of trapped protonated fluoroalkyl triazines

2007

Exploration of the Solid-State Sorption Properties of Shape-Persistent Macrocyclic Nanocarbons as Bulk Materials and Small Aggregates.

2020

Porous molecular materials combine benefits such as convenient processability and the possibility for atom-precise structural fine-tuning which makes them remarkable candidates for specialty applications in the areas of gas separation, catalysis, and sensing. In order to realize the full potential of these materials and guide future molecular design, knowledge of the transition from molecular properties into materials behavior is essential. In this work, the class of compounds termed cycloparaphenylenes (CPPs)-shape-persistent macrocycles with built-in cavities and radially oriented π-systems-was selected as a conceptually simple class of intrinsically porous nanocarbons to serve as a platf…