Effects of Aromatic Thiol Capping Agents on the Structural and Electronic Properties of CdnTen (n = 6,8 and 9) Quantum Dots

Thiols are efficient capping agents used for the synthesis of semiconductor and metal nanoparticles. Commonly, long-chain thiols are used as passivating agents to provide stabilization to nanoparticles. Theoretical methods rarely reported aromatic thiol ligands’ effects on small-sized CdTe quantum dots’ structural and electronic properties. We have studied and compared the structural and electronic properties of (i) bare and (ii) aromatic thiols (thiophenol, 4-methoxybenzenethiol, 4-mercaptobenzonitrile, and 4-mercaptobenzoic acid) capped CdnTen quantum dots (QDs). Aromatic thiols are used as thiol-radical because of the higher tendency of thiol-radicals to bind with Cd atoms. This work provides an understanding of how the capping agents affect specific properties. The results show that all aromatic thiol-radical ligands caused significant structural distortion in the geometries. The aromatic thiol-radical ligands stabilize LUMOs, stabilize or destabilize HOMOs, and decrease HOMO-LUMO gaps for all the capped QDs. The stabilization of LUMOs is more pronounced than the destabilization of HOMOs. We also studied the effect of solvent on structural and electronic properties. TD-DFT calculations were performed to calculate the absorption spectra of bare and capped QDs, and all the capping ligands resulted in the redshift of absorption spectra.

Evidence of sulfur centered hydrogen bond with sulfur atoms as a donor in aromatic thiols and aliphatic thiols on complexation with water using quantum mechanical methods

It has been more than a century since the discovery of hydrogen bonds, but the knowledge about its impact on day to day life of people is getting enhanced even now. It has a pivotal role in the stabilization of various biomolecules and subsequent bioactivity. Sulfur cantered hydrogen bond (SCHB), which is a weak interaction, has attracted the attention of many scientists in the last few decades. In this work, we report the nature of the SCHB between aliphatic/aromatic thiols and water. B3LYP-D3(BJ) with cc-pVTZ level was used for modeling the hydrogen bonded thiol-water complexes. Domain-based local pair natural orbitals coupled-cluster theory with single, double, and perturbative triple excitation DLPNO-CCSD(T) method was used for local energy decomposition analysis. QTAIM analysis helped to examine hydrogen bonds, weak non-covalent interactions, and the various electron density delocalization. Natural Bond Orbital (NBO) analysis explains the reason for the sulfur atom being the H-bond donor. Second-order perturbation energy from NBO findings supports the data obtained by LED and AIM calculations. Aromatic thiols form stronger hydrogen bonds than aliphatic thiols. The effect of substituents was also explored by studying aromatic systems with electron-withdrawing groups and donating groups. EDG substituted have more vital interaction, and EWG substituted thiols form stronger S-H…O hydrogen bonds.

Direct Access to S-Heterocycles by Scandium(III) Triflate Catalyzed Cyclization of Aromatic Thiols and Diols

A simple and environmentally friendly method to prepare S-heterocycles by cyclization of aromatic thiols and diols with H2O as a byproduct is described. The Sc(OTf)3-catalyzed dehydrative cyclizations of aromatic thiols and diols provided the corresponding thiopyran and thiophene derivatives. Control experiments were also performed to obtain insights into the reaction pathway

Origins of the photoinitiation capacity of aromatic thiols as photoinitiatiors: a computational study

In this work, we report the photophysical properties of three thiol derivatives, commonly used as photoinitiators in thiol–ene free radical polymerization, the ultimate goal being to rationalize the main reason behind the photoinitiation efficiency.