A dehydrogenative Heck annelation reaction of indolizine with diaryl acetylene via dual C–H bond cleavage was developed. Oxygen gas was employed as a clean oxidant in this catalysis under base-free conditions. Diarylpyrrolo[2,1,5-cd]indolizines were synthesized with high atom economy. In addition, kinetic isotope experiments provided evidence for C–H bond metalation of the 5-position of the indolizine as the rate-limiting step.

By introducing the second ligand 2,2’-bipy, a new copper(II) diphosphonate [Cu(H3L)(2,2′-bipy)] 1 (H5L = 1-hydroxyethylidenediphosphonate, 2,2′-bipy = 2,2′-bipyrimidine) has been hydrothermally synthesized and characterized by powder X-ray diffraction, elemental analysis, IR and TG-DTA. The single-crystal X-ray diffractions show that compound 1 possess a three-dimensional supramolecular structure, built from 1D chain via a single-bridge O–P–O in syn-anti fashion based on mononuclear unit [CuO3N2]. UV–vis spectra and the nature of electron transfer of 1 are investigated, and the experimental results are in agreement with the quantum chemistry calculation using the B3LYP/6-31G* method. Fluorescent measurements reveal that two emission peaks of 1 centered at 382.5 and 424.5 nm are mainly caused by intraligand π*–π emission state of the second ligands (375, 429.5 nm, λex = 235 nm). Results of electrochemical studies (CV) indicate a higher donor ability of 1.

Thiophene-based organic semiconductors used as the active components have received much attention. Their photoelectric properties can be easily tuned with various substitutions at different positions on molecular structures. Here, we synthesized series cyclopentadithiophene (CDT) derivatives with sulfur atoms at ortho- (o-CDT), meta- (m-CDT), and para-positions (p-CDT) of the bridge carbon. These CDT derivatives were substituted by carbonyl/dicyanomethylene at the bridge position and/or by phenyl groups at the α position, respectively. Due to the different conjugation extent and the variation of donor–acceptor (D–A) interaction originating from the change of sulfur atom position, diverse absorption spectra were observed. Especially for dicyanomethylene substituted o-CDT with phenyl as substitution group (DPCN-o-CDT), its absorption spectrum covers the whole region of visible light. Combining with the electrochemical behaviors and theoretical calculations, it was found that the sulfur atoms mainly contribute to the molecular conjugation in these CDT derivatives, especially for o-CDT derivatives. For phenyl groups, they primarily act as electron donor in m-CDT derivatives, and chiefly contribute to molecular conjugation in p-CDT derivatives, and simultaneously work as electron donor and conjugation component in o-CDT derivatives, respectively.

Based on the selectivity of deprotonation of 5,5′-bistrimethylsilyl-2,3′-bithiophene (4) in the presence of n-BuLi, three new cyclooctatetrathiophenes (COThs), COTh-1, COTh-2, and COTh-3 have been efficiently developed via intermolecular or intramolecular cyclizations. Their crystal structures clearly show that the different connectivity sequence of the thiophene rings in the molecules. The CV data and UV–vis absorbance spectra of COThs are also described. In addition, the time-dependent density functional theory (TDDFT) calculations accurately reproduce experimental observations and afford band assignment.