{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,12]],"date-time":"2026-02-12T10:36:50Z","timestamp":1770892610147,"version":"3.50.1"},"reference-count":51,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2021,2,12]],"date-time":"2021-02-12T00:00:00Z","timestamp":1613088000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100000001","name":"National Science Foundation","doi-asserted-by":"publisher","award":["CHE-1214102"],"award-info":[{"award-number":["CHE-1214102"]}],"id":[{"id":"10.13039\/100000001","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000001","name":"National Science Foundation","doi-asserted-by":"publisher","award":["CHE-1808120"],"award-info":[{"award-number":["CHE-1808120"]}],"id":[{"id":"10.13039\/100000001","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Molecules"],"abstract":"<jats:p>Isocyanoazulenes (CNAz) constitute a relatively new class of isocyanoarenes that offers rich structural and electronic diversification of the organic isocyanide ligand platform. This article considers a series of 2-isocyano-1,3-X2-azulene ligands (X = H, Me, CO2Et, Br, and CN) and the corresponding zero-valent complexes thereof, [(OC)5Cr(2-isocyano-1,3-X2-azulene)]. Air- and thermally stable, X-ray structurally characterized 2-isocyano-1,3-dimethylazulene may be viewed as a non-benzenoid aromatic congener of 2,6-dimethyphenyl isocyanide (2,6-xylyl isocyanide), a longtime \u201cworkhorse\u201d aryl isocyanide ligand in coordination chemistry. Single crystal X-ray crystallographic {Cr\u2013CNAz bond distances}, cyclic voltametric {E1\/2(Cr0\/1+)}, 13C NMR {\u03b4(13CN), \u03b4(13CO)}, UV-vis {d\u03c0(Cr) \u2192 p\u03c0*(CNAz) Metal-to-Ligand Charge Transfer}, and FTIR {\u03bdN\u2261C, \u03bdC\u2261O, kC\u2261O} analyses of the [(OC)5Cr(2-isocyano-1,3-X2-azulene)] complexes provided a multifaceted, quantitative assessment of the \u03c0-acceptor\/\u03c3-donor characteristics of the above five 2-isocyanoazulenes. In particular, the following inverse linear relationships were documented: \u03b4(13COtrans) vs. \u03b4(13CN), \u03b4(13COcis) vs. \u03b4(13CN), and \u03b4(13COtrans) vs. kC\u2261O,trans force constant. Remarkably, the net electron withdrawing capability of the 2-isocyano-1,3-dicyanoazulene ligand rivals those of perfluorinated isocyanides CNC6F5 and CNC2F3.<\/jats:p>","DOI":"10.3390\/molecules26040981","type":"journal-article","created":{"date-parts":[[2021,2,12]],"date-time":"2021-02-12T18:46:31Z","timestamp":1613155591000},"page":"981","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":5,"title":["Tuning \u03c0-Acceptor\/\u03c3-Donor Ratio of the 2-Isocyanoazulene Ligand: Non-Fluorinated Rival of Pentafluorophenyl Isocyanide and Trifluorovinyl Isocyanide Discovered"],"prefix":"10.3390","volume":"26","author":[{"given":"Mason D.","family":"Hart","sequence":"first","affiliation":[{"name":"Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, KS 66045, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"suffix":"Jr.","given":"John J.","family":"Meyers","sequence":"additional","affiliation":[{"name":"Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, KS 66045, USA"},{"name":"Department of Chemistry &amp; Physics, Clayton State University, 2000 Clayton State Blvd., Morrow, GA 30260, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1871-3469","authenticated-orcid":false,"given":"Zachary A.","family":"Wood","sequence":"additional","affiliation":[{"name":"Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, KS 66045, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Toshinori","family":"Nakakita","sequence":"additional","affiliation":[{"name":"Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, KS 66045, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jason C.","family":"Applegate","sequence":"additional","affiliation":[{"name":"Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, KS 66045, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Nathan R.","family":"Erickson","sequence":"additional","affiliation":[{"name":"Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, KS 66045, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Nikolay N.","family":"Gerasimchuk","sequence":"additional","affiliation":[{"name":"Department of Chemistry, Missouri State University, 901 S. National Ave., Springfield, MO 65897, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3389-9844","authenticated-orcid":false,"given":"Mikhail V.","family":"Barybin","sequence":"additional","affiliation":[{"name":"Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, KS 66045, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2021,2,12]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"711","DOI":"10.1002\/anie.198207113","article-title":"Building Bridges Between Inorganic and Organic Chemistry (Nobel Lecture)","volume":"21","author":"Hoffmann","year":"1982","journal-title":"Angew. Chem. Int. Ed."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1295","DOI":"10.1039\/C6CS00444J","article-title":"To each his own: Isonitriles for all flavors. 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