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Carbon−carbon bond cleavage of biphenylene was achieved with (C5Me5)M(C2H4)2 (M = Rh, Co) to give the bimetallic species (C5Me5)2M2(2,2‘-biphenyl). The isomorphous solid state X-ray structures of these complexes showed the biphenyl substrate to be σ-coordinated to one metal and η4-bound to the other. These complexes display dynamic behavior, interchanging the σ- and π-bonding. Variable-temperature NMR studies were performed on both binuclear species, and the energy barrier for interconversion of the two (C5Me5) fragments was calculated to be ΔG ⧧ (350 K) = 16.8 kcal/mol and ΔG ⧧ (248 K) = 11.4 kcal/mol for the rhodium and cobalt complexes, respectively. (C5Me5)2Rh2(2,2‘-biphenyl) reacted with CO to give (C5Me5)Rh(CO)2 and (C5Me5)Rh(CO)(2,2‘-biphenyl), while the cobalt analog gave (C5Me5)Co(CO)2 and fluorenone. (C5Me5)2Co2(2,2‘-biphenyl) gave (C5Me5)Co(PMe3)2 and (C5Me5)Co(PMe3)(2,2‘-biphenyl) when reacted with PMe3, as determined by X-ray crystallography of the latter complex. Both complexes were found to be resistant to hydrogenation.

Polymeric Quaternary Ammonium Compounds (polyQACs) comprise a broad class of materials with applications in medical implants, food processing, and surface sanitizing, amongst many others. These polymeric substances are especially promising due to their potent antibacterial activity and limited hemolytic toxicity. In particular, many polyQACs have superior therapeutic indices and a lower likelihood of developing antibacterial resistance in comparison to their monomers, making them ideal materials for wound dressings, catheters, and other biomedical applications. This review outlines the history and development, previous successes, current state of the research, and future directions of polyQACs in society.

The phytotoxin diplopyrone is considered to be the main phytotoxin in a fungus that is responsible for cork oak decline. A carbohydrate-based synthesis of the enantiomer of the structure proposed for diplopyrone has been developed from a commercially available derivative of d-galactose. Key steps in the synthesis are a highly stereoselective pyranose chain-extension based on methyltitanium, preparation of a vinyl glycoside via Isobe C-alkynylation-rearrangement/reduction, and RCM-based pyranopyran construction. Crystallographic and NMR analysis confirms an earlier report that the structure originally proposed for diplopyrone may require revision. Structural analogues were prepared for biological evaluation, the most promising being a pyranopyran nitrile synthesized from tri-O-acetyl-d-galactal by Ferrier cyanoglycosidation, Wittig chain extension, and lactonization. Biological assays revealed potent antibacterial activity for the nitrile analogue against common bacterial pathogens Edwardsiella ictaluri and Flavobacterium columnare that cause enteric septicemia (ESC) and columnaris disease, respectively, in catfish. The IC50 value of 0.002 against E. ictaluri indicates approximately 100 times greater potency than the antibiotic florfenicol used commercially for this disease. Phytotoxic activity for all three target compounds against duckweed was also observed. The antibiotic and phytotoxic activities of the new pyranopyrans synthesized in this study demonstrate the potential of such compounds as antibiotics and herbicides.