Evidence of Enhanced Conjugation in ortho-Arylene Ethynylenes with Transition Metal Coordination

• Published in: Journal of organic chemistry Vol. 77; no. 5; pp. 2571 - 2577
• Main Authors: Ren, Qianwei, Reedy, Cole G, Terrell, Eric A, Wieting, Joshua M, Wagie, Robert W, Asplin, Jake P, Doyle, Leah M, Long, Steven J, Everard, Michael T, Sauer, Jon S, Baumgart, Cassandra E, D’Acchioli, Jason S, Bowling, Nathan P
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 02-03-2012
• Subjects: Alkynes - chemistry; Chemistry; Coordination compounds; Exact sciences and technology; Heterocyclic compounds; Heterocyclic compounds with only one n hetero atom and condensed derivatives; Heterocyclic compounds with several n hetero atoms in the same ring, in separated rings or in fused rings; Inorganic chemistry and origins of life; Molecular Structure; Organic chemistry; Organometallic Compounds - chemical synthesis; Organometallic Compounds - chemistry; Palladium - chemistry; Preparations and properties; Pyrazines - chemistry; Pyridines - chemistry; Silver - chemistry; Molecular rigidity; Complexation; Nitrogen heterocycle; Palladium II; Pyrazine derivatives; Molecular interaction; Electron delocalization; Transition metal; Pyridine derivatives; Unsaturated compound; Polyynic compound; Acetylene derivative polymer; Bathochromism; Cations; Aromatic compound; Conjugated compound; Spectrophotometry; Silver I
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/jo300034h

The effective conjugation of ortho and ortho-alt-para-arylene ethynylenes, with appropriately positioned pyridine and pyrazine heterocycles, increases upon binding to Ag(I) and Pd(II) cations. Significant bathochromic shifts in the electronic spectra, witnessed upon introduction of these metal bridges, are consistent with enhanced electron delocalization in the unsaturated backbone. Control studies suggest that this electronic behavior is attributable exclusively (in the case of Ag(I)) or partially (in the case of Pd(II)) to conformational restrictions of the conjugated backbones.