Exploring Low Internal Reorganization Energies for Silicene Nanoclusters

High-performance materials rely on small reorganization energies to facilitate both charge separation and charge transport. Here, we performed DFT calculations to predict small reorganization energies of rectangular silicene nanoclusters with hydrogen-passivated edges denoted by H-SiNC. We observe that across all geometries, H-SiNCs feature large electron affinities and highly stabilized anionic states, indicating their potential as n-type materials. Our findings suggest that fine-tuning the size of H-SiNCs along the zigzag and armchair directions may permit the design of novel n-type electronic materials and spinctronics devices that incorporate both high electron affinities and very low internal reorganization energies.Comment: 25 pages, 6 figure

Detection of Multiconfigurational States of Hydrogen-Passivated Silicene Nanoclusters

Utilizing density functional theory (DFT) and a complete active space self-consistent field (CASSCF) approach,we study the electronic properties of rectangular silicene nano clusters with hydrogen passivated edges denoted by H-SiNCs (<i>n</i>_z,<i>n</i>_a), with <i>n</i>_z and <i>n</i>_a representing the zigzag and armchair directions, respectively. The results show that in the <i>n</i>_z direction, the H-SiNCs prefer to be in a singlet (<i>S</i> = 0) ground state for <i>n</i>_z > <i>n</i>_a. However, a transition from a singlet (<i>S</i> = 0) to a triplet (<i>S</i> = 1) ground state is revealed for <i>n</i>_a > <i>n</i>_z. Through the calculated Raman spectrum, the <i>S</i> = 0 and <i>S</i> = 1 ground states can be observed by the <i>E</i>_2<i>g</i> (G) and <i>A</i> (D) Raman modes. Furthermore, H-SiNC clusters are shown to have HOMO–LUMO (HL) energy gaps, which decrease as a function of <i>n</i>_a and <i>n</i>_z for <i>S</i> = 0 and <i>S</i> = 1 states. The H-SiNC with a <i>S</i> = 1 ground state can be potentially used for silicene-based spintronic devices

High‑<i>T</i>_g Functional Aromatic Polymers

A novel series of linear, high-molecular-weight polymers and copolymers were synthesized by one-pot, metal-free superacid-catalyzed polymerization of aliphatic 1,2-diketones (2,3-butanedione (<b>1a</b>), 2,3-hexadione (<b>1b</b>), 3,4-hexadione (<b>1c</b>), 2,3-butanedione monoxime (<b>1d</b>), pyruvic acid (<b>1e</b>), 1,4-dibromo-2,3-butanedione (<b>1f</b>), 2-bromopyruvic acid (<b>1g</b>), and methyl-3,3,3-trifluoropyruvate (<b>1h</b>) with linear, nonactivated, multiring aromatic hydrocarbons terphenyl (<b>A</b>), biphenyl (<b>B</b>), fluorene (<b>C</b>), and <i>N</i>-ethyl carbazole (<b>D</b>). Depending on the reaction system, the polymerizations were carried out as stoichiometric or non stoichiometric, with direct or inverse monomer addition. Copolymers were obtained by polymerization of 1,2-diketones with a mixture of aromatic hydrocarbons. In the course of the polymerization only one carbonyl group of a 1,2-diketone reacts to form C–C bonds with aromatic fragments while the other functional groups (including the second carbonyl group) are incorporated unchanged into polymer chain. The polymerizations performed at room temperature in the Brønsted superacid CF₃SO₃H (TFSA) and in a mixture of TFSA with methylene chloride or trifluoroacetic acid (TFA) tolerant of carbonyl, acetyl, <i>N</i>-oxime, carboxy, methoxy, and bromomethyl groups. The polymers obtained were soluble in most common organic solvents, and flexible transparent, colorless films could be cast from the solutions. ¹H and ¹³C NMR analyses of the polymers synthesized revealed high regio-selectivity of the polymerizations and yielded linear structures with para-substitution in the phenylene fragments of the main chains. An electron affinity (<b>EA</b>) of the carbonyl component and the heterolytic C–O bond dissociation energy (<b>DE</b>) in carbinol <b>3</b> (correlating with the activation energy of carbocation <b>4</b> formation) have been used to rationalize the reactivity of carbonyl components. The calculations show the following reactivity order of the diketones. <b>1f</b> > <b>1g</b> ≈ <b>1e</b>> <b>1a</b>> <b>1d</b> > <b>1h</b>> <b>1b</b>><b>1c</b> which is totally in agreement with the experimental data. The new functional polymers obtained demonstrate good processability, high <i>T</i>_g and thermal stability. Unexpected white light emission was observed for polymer <b>2gA</b>