Substituent

About: Substituent is a research topic. Over the lifetime, 42877 publications have been published within this topic receiving 516716 citations. The topic is also known as: side chain & side group.

Highly Disordered Polymer Field Effect Transistors: N-Alkyl Dithieno[3,2-b:2′,3′-d]pyrrole-Based Copolymers with Surprisingly High Charge Carrier Mobilities

Abstract: A series of novel electroactive and photoactive conjugated copolymers based on N-alkyl dithieno[3,2-b:2′,3′-d]pyrroles (DTP) and thiophene (TH) units (DTP-co-THs) were synthesized using a Stille coupling reaction and exhibited molecular weights of 1.6 × 104 to 5.0 × 104 g/mol. The incorporation of soluble substituted thiophenes and planar DTP units resulted in low band gap, highly conductive polymers. DTP-co-THs exhibited excellent solubility in common organic solvents and formed high-quality films. Optical characterization revealed that the band gaps of DTP-co-THs were between 1.74 and 2.00 eV, lower than regioregular poly(3-alkylthiophenes). Electrochemical characterization showed that the HOMO energy levels of DTP-co-THs are between −4.68 and −4.96 eV. When doped, DTP-co-THs exhibited high conductivities up to 230 S/cm with excellent stability. The different thiophene substituent patternsʼ effect on the polymers’ optical and electronic properties was then examined by density functional theory computati...

Steric Effects in the Ground and Excited States of Cu(NN)2+ Systems

Abstract: This investigation focuses on a series of pseudotetrahedral complexes of the form Cu(NN)2+, where NN denotes a 1,10-phenanthroline ligand with alkyl substituents in the 2 and 9 positions and the counterion is PF6-. In these copper(I) systems, steric effects are of considerable interest because the electronic configuration predisposes the reactive charge-transfer excited state to undergo a flattening distortion or to add a fifth ligand. Both effects lead to emission quenching and a shorter excited-state lifetime. Bulky substituents inhibit these processes, but the spatial distribution of the atoms involved is more important than the total molecular volume in determining the influence of a substituent. According to the results of this study, the effective size decreases in the following order: sec-butyl > neopentyl > n-octyl ≈ n-butyl > methyl. In conjunction with the electrochemical data, the absorption and the emission spectra reveal three kinds of steric effects: (1) Clashes between substituents on opp...