Modulating the Photophysical Properties and Electron Transfer Rates in Diketopyrrolopyrrole-Based Coordination Polymers.

Molecular self-assembly through noncovalent interactions is a particularly efficient approach to fine-tune the optoelectronic and photophysical properties of electroactive materials. In metal-ligand coordination polymers, the final properties of the assemblies are directly related to the nature of the metal-ligand interaction. To probe for such influence on the photophysical properties of electroactive materials, a series of coordination polymers based on a well-known organic dye, diketopyrrolopyrrole, was prepared through coordination of a terpyridine-containing monomer with various metal sources, including iron, cobalt, zinc, and manganese. The resulting supramolecular polymers were characterized through multiple techniques, including UV-vis and fluorescence spectroscopy, time-correlated single-photon counting, and femtosecond transient absorption spectroscopy to reveal the impact of the metal source on the final photophysical properties of coordination polymers. As expected, important variations were found between different coordination polymers in terms of absorption, fluorescence kinetics, and electron transfer rate. While iron and cobalt-containing polymers showed ultrafast electrons transfer rates, assemblies from manganese were shown to be much less efficient, confirming the importance of metal centers. This detailed fundamental study unravels some important relationships between metal-ligand interactions, supramolecular self-assembly, and photophysical properties, ultimately leading to new avenues for the design of functional polymers based on organic dyes.

2,6-Bis(benzimidazol-2-yl)pyridine complexes of group 14 elements.

Treatment of MCl2 (M = Ge or Sn) with 2,6-bis(benzimidazol-2-yl)pyridine (G-BZIMPY, G = NBn, N(3,5-CF3)Bn, NAllyl and O) yielded the self-ionization products [G-BZIMPYMCl][MCl3] (1-6) in high yields (75-98%). Reduction reactions are examined and the nickel complexes 8 and 9 ([(NBn-BZIMPY)2Ni][MCl3]2) are isolated from the reaction of Ni(COD)2 with 1 and 2 respectively. [NBn-BZIMPYSnCl][SnCl3] shows a significantly stronger MLCT band in the UV-vis absorption spectrum than its germanium counterparts, with germanium complexes exhibiting negative solvatochromism that is not observed in tin complexes.

Recent Advances in Mechanically Robust and Stretchable Bulk Heterojunction Polymer Solar Cells.

Organic bulk heterojunction solar cells are promising candidates as future photovoltaic technologies for large-scale and low-cost energy production. It is, therefore, not surprising that research on the design and preparation of these types of organic photovoltaics has attracted a lot of attention since the last two decades, leading to constantly growing values of energy conversion and efficiency. Combined with the possibility of a large-scale production via roll-to-roll printing techniques, bulk heterojunction solar cells enable the fabrication of conformable, light-weight and flexible light-harvesting devices for point-of-use applications. This perspective review will highlight the recent advances toward mechanically robust and intrinsically stretchable bulk heterojunction solar cells. Mechanically robust fullerene-based and all-polymer devices will be presented, as well as a comprehensive overview of the recent challenges and characterization techniques recently developed to overcome some of the challenges of this research area, which is still in its infancy.

Synthesis of Heavy Dicyanamide Homologues from Air-Stable Precursors.

A convenient synthesis of dicyanophosphide and dicyanoarsenide anions is reported. These heavy homologues of the long-known and fundamentally important dicyanamide anion were formed through the nucleophilic displacement of bis(diphenylphosphino)ethane (dppe) from the pnictogen+ transfer agents [dppePn][BPh4 ] (Pn=P, As) by exposure to cyanide salts. The protocol requires three synthetic steps from commercially available materials and the [dppePn][BPh4 ] salts are remarkably temperature, air, and moisture stable. All products have been fully characterized by spectroscopic methods and by single-crystal X-ray diffraction, and the electronic structures of the DCPn anions have been assessed computationally.