{
  "abstract": "Cyanine dyes are one of the most important classes of polymethine dyes because of their unique and highly tunable optical properties that can be adjusted through structural modifications. They play a central role as high-value-added functional dyes across numerous cutting-edge technologies. Unsymmetric cyanines exhibit optical properties that differ markedly from their symmetric counterparts. Most unsymmetric dimethine cyanines presented in the literature are indole-based, displaying strong fluorescence and often used as biological markers. However, only a few examples of dimethine cyanine dyes deviating from this common indole-based model are reported. In this work, a new family of unsymmetric dimethine cyanines incorporating an indolizine donor unit and different cationic heterocycles are presented (1a-1d). A comprehensive understanding of the structure and electronic properties of these new cyanine derivatives was achieved through the combined use of synthesis, NMR and UV-Vis spectroscopies, X-ray diffraction, and (TD)DFT calculations. These dyes absorb in the 588-705 nm range and are weakly fluorescent in solution but emit up to 914 nm with decent quantum yields in the solid-state. Despite their formal lack of symmetry, compounds 1b-1d exhibit a cyanine-like behaviour, including small bond-length alternation, narrow and vibronically structured absorption bands, small Stokes shifts, and negligible solvatochromism. In contrast, the quinolinium derivative 1a displays a markedly different behavior, with a decreased cyanine-like character, partial ground-state symmetry breaking, and enhanced solvatochromic absorption effect. These results demonstrate that indolizine constitutes an effective building block for the design of unconventional unsymmetric cyanines that retain a remarkably symmetric electronic structure and cyanine-like photophysical properties despite their formally unsymmetrical constitution.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": null,
  "author_total": 4,
  "authors": [
    {
      "name": "Marie Lucas"
    },
    {
      "name": "Erwann Jeanneau"
    },
    {
      "name": "Josene Toldo"
    },
    {
      "name": "Yann Bretonnière"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/bmcg4nts1mckv.bib",
  "cited_by": 0,
  "doi": "10.1016/j.dyepig.2026.114075",
  "fulltext_url": null,
  "id": "bmcg4nts1mckv",
  "issns": [
    "0143-7208"
  ],
  "landing_url": "https://hal.science/hal-05761515v1",
  "language": "en",
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "hal",
      "0.chim"
    ],
    [
      "hal",
      "1.chim.orga"
    ],
    [
      "hal",
      "1.chim.theo"
    ],
    [
      "openalex",
      "2505|Luminescence and Fluorescent Materials"
    ]
  ],
  "openalex": "W7172231453",
  "pdf_url": "https://hal.science/hal-05761515/document",
  "pmcid": null,
  "pmid": null,
  "published": "2026-08-02",
  "publisher": "Elsevier",
  "ris": "https://research.draconitic.com/paper/bmcg4nts1mckv.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:17:39Z",
      "native_id": "hal-05761515",
      "source": "hal",
      "url": "https://hal.science/hal-05761515v1"
    }
  ],
  "subjects": [
    {
      "field": "chemistry",
      "origin": "hal:1.chim.orga",
      "subfield": "organic"
    },
    {
      "field": "chemistry",
      "origin": "hal:1.chim.theo",
      "subfield": "theoretical"
    }
  ],
  "title": "Indolizine-derived unsymmetric dimethine cyanines with electronic symmetry, strong π-delocalization, and nearinfrared solid-state emission",
  "title_text": "Indolizine-derived unsymmetric dimethine cyanines with electronic symmetry, strong π-delocalization, and nearinfrared solid-state emission",
  "type": "peer-reviewed",
  "updated_at": "2026-10-30T12:17:39Z",
  "url": "https://research.draconitic.com/paper/bmcg4nts1mckv",
  "venue": "Dyes and Pigments",
  "versions": []
}