{
  "abstract": "Single crystals of the [Ru(SO2)(NH3)4X]Y family of complexes are promising photoswitches or photoactuators; they respond structurally to visible light, undergoing SO2 linkage photoisomerization with high spatiotemporal precision. However, the SO2 photoconversion efficiency (PCE) varies markedly with the trans-ligand X and no unifying molecular design principle is yet available. This study addresses this knowledge gap by performing electronic-structure calculations on 11 respective crystal structures of these complexes using reference crystal structures characterized by single-crystal X-ray diffraction under light irradiation. We focus on 4 structural archetypes of [Ru(SO2)(NH3)4X][tosylate]2, where X = H2O (1), 3-F-pyridine (2), 3-Cl-pyridine (3), and 3-Br-pyridine (4), to elucidate how the trans-ligands control the Ru-centered electronic rearrangement upon photoexcitation. The dark-state projected densities of states of these crystal structures are qualitatively similar across the series, exhibiting [Ru]-S π-bonding and [Ru]-X π/σ interactions. By contrast, electronic-structure calculations using time-dependent density functional theory reveal distinct photoexcited-state behavior: in 1, photoexcitation populates an antibonding dyz-py orbital, weakening the [Ru]-S bond and lowering the SO2 photoisomerization barrier; in 2-4, photoexcitation simultaneously populates this antibonding orbital and depopulates its bonding counterpart, weakening the [Ru]-S bond substantially more to afford a correspondingly higher PCE than in 1. Response charge-density analyses visualize the corresponding photoinduced charge redistribution in real space, consistent with the finer ordering of the PCE: 3 < 2 < 4. We additionally propose the Ru d-band center as a descriptor for PCE: within a common class of trans-ligand, the PCE tends to decrease as the d-band center shifts toward the Fermi level, as shown here for ten pyridyl-ligated structures, although other factors also contribute to the photoisomerization process. Together, these results provide a mechanistic account of photoexcited-state changes in the electronic structure of [Ru(SO2)(NH3)4X]Y complexes and suggest a practical screening metric for the rational molecular design of this family of high-PCE photoresponsive single crystals for quantum photosensing applications.",
  "abstract_shown": true,
  "affiliations": [
    "Ray Dolby Centre, Cavendish Laboratory, Department of Physics, University of Cambridge, J. J. Thomson Avenue, CambridgeCB3 0US, U.K."
  ],
  "article_type": "research article",
  "arxiv": null,
  "author_total": 2,
  "authors": [
    {
      "affs": [
        0
      ],
      "name": "Haoqian Zhou"
    },
    {
      "affs": [
        0
      ],
      "name": "Jacqueline M Cole",
      "orcid": "0000-0002-1552-8743"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/fber76aab7d57.bib",
  "cited_by": 0,
  "doi": "10.1021/acs.jpclett.6c02623",
  "fulltext_url": "https://europepmc.org/articles/PMC13656775",
  "id": "fber76aab7d57",
  "issns": [
    "1948-7185"
  ],
  "landing_url": "https://europepmc.org/article/MED/42917767",
  "language": "eng",
  "licence": "CC-BY",
  "licence_label": "CC BY",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "openalex",
      "2505|Photochromic and Fluorescence Chemistry"
    ]
  ],
  "openalex": "W7214222362",
  "pdf_url": "https://europepmc.org/articles/PMC13656775?pdf=render",
  "pmcid": "PMC13656775",
  "pmid": "42917767",
  "published": "2026-10-01",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/fber76aab7d57.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:20:36Z",
      "native_id": "MED:42917767",
      "source": "europepmc",
      "url": "https://europepmc.org/article/MED/42917767"
    }
  ],
  "subjects": [
    {
      "field": "chemistry",
      "origin": "openalex:2505|Photochromic and Fluorescence Chemistry",
      "subfield": "materials-polymers"
    }
  ],
  "title": "Dark- and Photoexcited-State Electronic Structures of [Ru(SO2)(NH3)4X]Y Complexes and Their Relation to SO2 Photoconversion Efficiency.",
  "title_text": "Dark- and Photoexcited-State Electronic Structures of [Ru(SO2)(NH3)4X]Y Complexes and Their Relation to SO2 Photoconversion Efficiency.",
  "type": "peer-reviewed",
  "updated_at": "2026-10-30T12:20:36Z",
  "url": "https://research.draconitic.com/paper/fber76aab7d57",
  "venue": "The journal of physical chemistry letters",
  "versions": []
}