Density functional theory (DFT) calculations are useful to model orbital energies of conjugated polymers, yet discrepancy between theory and experiment exist. Here we evaluate a series of relatively straightforward calculation methods using the standard Gaussian 09 software package. Five calculations were performed on 22 different conjugated polymer model compounds at the B3LYP and CAM-B3LYP levels of theory and results compared with experiment. Chain length saturation occurs at approximately 6 and 4 repeat units for homo- and donor–acceptor type conjugated polymers, respectively. The frontier orbital energies are better approximated using B3LYP than CAM-B3LYP, and the HOMO energy can be reasonably correlated with experiment [mean signed error (MSE) = 0.22 eV]. The LUMO energies, however are poorly correlated (MSE = 0.59 eV), and we show that the molecular orbital energy of the triplet state gives a much better estimate of the experimentally determined LUMO level (MSE = −0.13 eV).

Perfluoroaryl-substituted tellurophenes act as anion receptors through noncovalent chalcogen bonding interactions. Linking two tellurophenes through an ethynylene group results in a significant level of chelate cooperativity, thus demonstrating that chalcogen bonding can be used to achieve multidentate anion recognition.

The development of high-carbon-content polymers for optoelectronics is an area of intense research; however, carbon-rich materials have certain limitations that arise from their composition. Some of these limitations can be overcome by the judicious incorporation of heavier elements which do not significantly change the carbon content to a point where it adversely affects cost and processability. Here we examine the use of tellurium as a heavy atom in the design of optoelectronic polymers. Group 16 atom (O, S, Se, Te) substitution is a promising strategy for the development of high performance materials for organic electronic applications. The use of tellurium in place of selenium or sulfur in conjugated polymers lends new properties to these materials such as red-shifted optical absorption, high polarizability, high dielectric constant, and strong intermolecular interactions. These properties are favorable for organic photovoltaics (OPVs) and organic field effect transistors (OFETs). In particular, extending the absorption range to the near-IR allows for more efficient solar harvesting since low-energy photons are most abundant. Additionally, strong Te−Te interactions lead to enhanced interchain electronic coupling, which is expected to facilitate charge transport. The use of polymers containing tellurophene, the tellurium analogue of the well-studied thiophene, has only recently begun to emerge in the literature. New synthetic routes have been developed, and there now exist a handful of tellurophene-containing polymers that have been synthesized and used to fabricate OPVs and OFETs. Their performance in OPVs has not surpassed that of their lighter chalcogen analogues; however, the use of tellurophene-containing materials is a young field, and continued efforts in the development of new materials and device optimization should lead to improved performance. In this Perspective we discuss the current status of tellurium-containing polymers in terms of their synthesis, properties, and performance. We highlight the challenges that have been overcome thus far and emphasize those that should be the focus of future work. This includes overcoming synthetic challenges and developing an understanding of the current limitations in device performance with tellurium-containing polymers through studies of materials properties and excited state dynamics. We also suggest new applications and directions for tellurium-containing materials beyond OPVs and OFETs.

This study introduces small molecule tellurophenes that can undergo photoreductive elimination. A tellurophene compound with strong light absorption properties and extended π-conjugation, 2,5-bis[5-(N,N'-dihexylisoindigo)]tellurophene (1), has been synthesized. Halogen oxidative addition to the tellurium center from various halogen sources gives the dibromo- (1Br2) and dichloro- (1Cl2) adducts, leading to a red-shift in the optical absorption properties. In the presence of excess opposing halogen, 1Br2 and 1Cl2 can interconvert, with equilibrium favoring the dichlorotellurophene adduct. Reductive elimination reactions were studied using optical absorption spectroscopy, NMR spectroscopy, thermogravimetric analysis, and matrix-assisted laser desorption/ionization (MALDI) analysis. Thermal reductive elimination from 1Br2 and 1Cl2 occurs in the solid-state to restore 1. Photoreductive elimination occurs under irradiation with green (505 nm) light in solution in the presence of a halogen trap with some decomposition. This is the first example of photoreductive elimination from a mononuclear tellurophene complex.

We present the reactivity and photochemistry of 2,5-diphenyltellurophene. A change in oxidation state from Te(ii) to Te(iv) occurs by oxidative addition of bromine, chlorine, and fluorine from appropriate halogen sources. Photoreductive halogen elimination is demonstrated using optical absorption spectroscopy and NMR spectroscopy. The photodebromination reaction occurs with 16.9% quantum yield, the highest value for any Te compound. Photoreductive elimination of chlorine and fluorine occurs with quantum yields of 1.6% and 2.3%, respectively, albeit with less efficient halogen trapping when an organic trap is used. Improved fluorine trapping was achieved using water, allowing for much cleaner photodefluorination. This is the first example of photodefluorination from a tellurium compound.