Shining Light on Organometallic Chemistry
2024; American Chemical Society; Volume: 43; Issue: 16 Linguagem: Inglês
10.1021/acs.organomet.4c00309
ISSN1520-6041
AutoresDebashis Adhikari, Sun Dongbang, Xuefeng Jiang, Dominik Munz,
Tópico(s)Radical Photochemical Reactions
ResumoInfoMetricsFiguresRef. OrganometallicsVol 43/Issue 16Article This publication is free to access through this site. Learn More CiteCitationCitation and abstractCitation and referencesMore citation options ShareShare onFacebookX (Twitter)WeChatLinkedInRedditEmailJump toExpandCollapse Editor's PageAugust 26, 2024Shining Light on Organometallic ChemistryClick to copy article linkArticle link copied!Debashis Adhikari*Debashis AdhikariDepartment of Chemical Sciences, Indian Institute of Science Education and Research Mohali, Mohali, Punjab 140306, India*Email for D.A.: [email protected]More by Debashis AdhikariView Biographyhttps://orcid.org/0000-0001-8399-2962Sun Dongbang*Sun DongbangDepartment of Chemistry, Sogang University, Baebeom-ro 35, Mapo-gu, Seoul 04107, Republic of Korea*Email for S.D.: [email protected]More by Sun DongbangView Biographyhttps://orcid.org/0000-0001-6599-3603Xuefeng Jiang*Xuefeng JiangShanghai Key Laboratory of Green Chemistry and Chemical Processes, School of Chemistry and Molecular Engineering, East China Normal University, North Zhongshan Road 3663, Shanghai 200062, People's Republic of China*Email for X.J.: [email protected]More by Xuefeng JiangView Biographyhttps://orcid.org/0000-0002-1849-6572Dominik Munz*Dominik MunzCoordination Chemistry, Saarland University, Campus C4.2, 66123 Saarbrücken, Germany*Email for D.M.: [email protected]More by Dominik MunzView Biographyhttps://orcid.org/0000-0003-3412-651XOpen PDFOrganometallicsCite this: Organometallics 2024, 43, 16, 1659–1661Click to copy citationCitation copied!https://pubs.acs.org/doi/10.1021/acs.organomet.4c00309https://doi.org/10.1021/acs.organomet.4c00309Published August 26, 2024 Publication History Received 9 July 2024Published online 26 August 2024Published in issue 26 August 2024editorialCopyright © Published 2024 by American Chemical Society. This publication is available under these Terms of Use. Request reuse permissionsThis publication is licensed for personal use by The American Chemical Society. ACS PublicationsCopyright © Published 2024 by American Chemical SocietySubjectswhat are subjectsArticle subjects are automatically applied from the ACS Subject Taxonomy and describe the scientific concepts and themes of the article.LigandsLightPhotocatalystsPhotochemical synthesisPhotochemistrySPECIAL ISSUEThis article is part of the Shining Light on Organometallic Chemistry: Synthesis, Mechanisms, and Applications Driven by Photochemistry special issue.Solar energy conversion drives life on Earth. Artificial photochemistry, on the other hand, has traditionally targeted inorganic semiconductors, organic transformations as exemplified by thermally forbidden [2 + 2] cycloadditions and the activation of diazo- and azide functional groups, metal-organic coordination compounds such as [Ru(bipy)3]2+ and the Creutz–Taube ion, and theory-/spectroscopy-driven approaches. Hence, organometallic photochemistry has long been limited to essentially simple metal–ligand bond cleavage reactions. (1) Interdisciplinary by nature, organometallic photochemistry matured over the last 20 years to represent now its own field of research. This development was driven mainly by two advancements: These are (i) research on strongly bonded C-donor ligands, which allowed for the synthesis of stable complexes with large ligand-field splitting and long-lived excited states, thus rendering them suitable chromophores/luminophores for photocatalysis, photovoltaics, and organic light-emitting devices (OLEDs), and (ii) the enhanced understanding of open-shell reaction mechanisms, which paved the way for photoredox catalysis, enabling previously unfeasible "dream reactions". In fact, abundant photoredox-catalytic protocols nowadays rely on organometallic sensitizers. Particularly successful photocatalysts are tris(2-phenylpyridine)iridium and its derivatives. This 3-fold cyclometalated complex had been first synthesized in high yield by Watts and colleagues in 1991. (2) The strong spin–orbit coupling induced by the heavy element iridium largely eliminates the spin-forbidden nature of the phosphorescent transitions in this complex, thus rendering it suitable for a vast range of applications requiring high quantum yields of excited states with long lifetime at room temperature. Although this complex did not receive vast attention until subsequent work by the Thompson group in 2001, (3) it is now one of the main workhorses in the field, as demonstrated by the contribution by Dang and Teets featured herein (10.1021/acs.organomet.3c00491). Despite their superior photophysical properties, the major current challenge in this field is the desire to replace heavy and noble metals such as iridium, platinum, and gold with earth-abundant 3d or main-group metals. (4) While there is still a long way to go, modern organometallic chemistry is developing solutions, as exemplified by Heinze and colleagues' contribution to this special issue, which reports on spin-flip emissive cyclometalated chromium(III) complexes (10.1021/acs.organomet.4c00075). A complementary approach is presented by the Haas group, who reports how the irradiation of acyl silanes induces Brook-type rearrangement reactions (10.1021/acs.organomet.3c00531).This special issue "Shining Light on Organometallic Chemistry: Synthesis, Mechanisms, and Applications Driven by Photochemistry" celebrates current photochemistry with molecular organometallic compounds. The feature articles mentioned above represent the two directions of the special issue: six contributions address (i) the design and characterization as well as application of luminescent organometallics, and four contributions target (ii) photo-organometallic approaches to the synthesis of fine chemicals.Stipurin and Strassner studied cyclometalated N-heterocyclic C∧C* platinum complexes, supported by bis(pyridyl)- and bis(pyrazolyl)borate ligands (10.1021/acs.organomet.3c00532). Demonstrating the versatility of the field, this contribution comprises air-sensitive organometallic synthesis and structural characterization in the solid state, spectroscopy (UV–vis absorption/emission in solution and solid state, cyclic and differential pulse voltammetry, time-resolved single photon counting TCSPC) and quantum chemical calculations. The authors find that the emissive properties are controlled by the organometallic C∧C* moiety, whereas the ancillary N-donor-borate ligands tune only the emission quantum yields (10–90%). Corresponding characterization techniques also find use in Stein, Förster, and Heinze's contribution on tris-cyclometalated P∧C and N∧C chromium(III) spin-flip emitters (10.1021/acs.organomet.4c00075). These emitters do not harness common charge-transfer transitions, yet promote metal-centered 4A2 ← 2E/2T1 spin-flip emission in pseudo-octahedral coordination. Key to this design concept are the strong-field phenyl ligands, which prevent excited state deactivation via back-intersystem crossing. In fact, the pendant amine and phosphine ligands are labile in solution, thus hampering their usefulness in optical applications of such chromium(III) complexes. Romanov, Linnolahti, and colleagues present an investigation on diamido-carbene (DAC)-supported gold(I) emitters (10.1021/acs.organomet.3c00360). Peculiar ring-opening of the carbene was observed in the presence of KOtBu, thereby affording an intriguing Au3 triangle, whereby each gold ion is coordinated by an acyclic, N,O-substituted carbene. The corresponding (DAC)AuX precursor molecules were found to not exhibit a ligand-centered, dark triplet 3LC state as the lowest in energy triplet state. This prompted the authors to move away from conventional NHC use for gold(I) emitters and to foresee a brighter future for strong acceptor carbenes just as the DAC itself. Strassert et al. present two detailed investigations on 1O2 photosensitization by CNN and NNN pincer-type ligand supported platinum(II), palladium(II) and related rhenium(I) complexes (10.1021/acs.organomet.3c00539; 10.1021/acs.organomet.3c00540). The switch from platinum to palladium results in weaker ligand field splitting and reduced spin–orbit coupling, thereby boosting excited-state lifetimes without luminescence at room temperature, and enabling dual-emission in the case of thiophenyl decoration. In vitro (photo)cytotoxicity studies conducted on human telomerase reverse transcriptase-immortalized cells demonstrated their potential for photodynamic therapy. The contribution by the Haas group (10.1021/acs.organomet.3c00531) presents a study on mono- and bis(acyl)polysilanes and their photoinduced Brook-type rearrangement via transient silenes, thus complementing the other contributions targeting d-block complexes from a p-block perspective.Dongbang reviewed the latest advancements in metalla-photoredox-catalyzed C(sp3)–C(sp3) cross-coupling, which has opened important new molecular space (10.1021/acs.organomet.3c00537). Specific emphasis is put on the mode of activation of the C(sp3) precursors, namely via metal-based reduction, oxidation by the photocatalyst, hydrogen or halogen atom transfer, or photosensitization leading to subsequent homolytic bond cleavage. The specific modes of activation are then used to systematically categorize the literature precedents, hence presenting the field in a concise and detailed manner. Exploring a related theme of photocatalyzed cross-coupling, Xue et al. discuss a nickel-based photocatalyst that enables the sulfamidation of aryl chlorides with soluble and mild organic amines as bases (10.1021/acs.organomet.3c00506). This photochemical C–N coupling reaction proceeds selectively even in the presence of multiple NH2 groups and presents unprecedented substrate scope with electron-rich (hetero)aryl chlorides, including the direct synthesis of sulfonamide drug molecules. The photohydrogenation of ketones, aldehydes, and imines under blue light is described by Dang and Teets (10.1021/acs.organomet.3c00491). Using the strong excited-state reducing power of cyclometalated Ir(2-phenylpyridine)2(nacnac) in combination with the sacrificial hydrogen donor BIH (1,3-dimethyl-2,3-dihydro-2-phenylbenzimidazole) prevents the undesired homocoupling to diols and diamines and switches the selectivity instead to C═N/C═O hydrogenation with reduction potentials as negative as −2.57 V versus the Fc/Fc+ redox couple. Meng, Ji, and Jiang describe a metal-oxo uranyl photocatalyst that harnesses a ligand-to-metal charge transfer (LMCT) excitation with high oxidation potential (E° = +2.6 V vs SHE) to achieve the deprotection of benzyl groups under oxidative conditions (10.1021/acs.organomet.4c00080). The catalytic procedure is straightforward, scales well, is compatible with moisture and air, tolerates nitro, cyano, phenol, and carbonyl functional groups, and hence presents a convenient route to pharmaceuticals and organic materials.This special issue shines light on photoactive organometallic complexes and their applications as photoredox catalysts. We think that this collection provides an overview on the current achievements and limitations in the field and hope that it sparks the excitement of junior researchers to discovering future breakthroughs for cost-effective and sustainable solar energy conversion. The future is shining bright for organometallics!Author InformationClick to copy section linkSection link copied!Corresponding AuthorsDebashis Adhikari, Department of Chemical Sciences, Indian Institute of Science Education and Research Mohali, Mohali, Punjab 140306, India, https://orcid.org/0000-0001-8399-2962, Email: [email protected]Sun Dongbang, Department of Chemistry, Sogang University, Baebeom-ro 35, Mapo-gu, Seoul 04107, Republic of Korea, https://orcid.org/0000-0001-6599-3603, Email: [email protected]Xuefeng Jiang, Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of Chemistry and Molecular Engineering, East China Normal University, North Zhongshan Road 3663, Shanghai 200062, People's Republic of China, https://orcid.org/0000-0002-1849-6572, Email: [email protected]Dominik Munz, Coordination Chemistry, Saarland University, Campus C4.2, 66123 Saarbrücken, Germany, https://orcid.org/0000-0003-3412-651X, Email: [email protected]NotesViews expressed in this editorial are those of the authors and not necessarily the views of the ACS.BiographiesClick to copy section linkSection link copied!Debashis AdhikariHigh Resolution ImageDownload MS PowerPoint SlideDebashis Adhikari is currently an associate professor of Chemistry in IISER Mohali, India. He earned his Ph.D. in inorganic chemistry from Indiana University, Bloomington, and performed postdoctoral research in Northwestern University, Evanston. His group focuses on redox-active ligands applied towards homogeneous catalysis, borrowing hydrogen reactions, and making strong photo-oxidants and reductants under visible light.Sun DongbangHigh Resolution ImageDownload MS PowerPoint SlideSun Dongbang (Ph.D. 2020) is an assistant professor in the Department of Chemistry at Sogang University, South Korea. Her Ph.D. and postdoctoral studies have centered around total synthesis of natural products and methodology development using transition metals to construct structurally complex motifs. The current group's research interests lie in the development of new transition-metal catalysis using earth-abundant metals and photoredox-catalyzed synthetic methods.Xuefeng JiangHigh Resolution ImageDownload MS PowerPoint SlideXuefeng Jiang (Ph.D. 2008) is a Professor for Organic Chemistry at East China Normal University, China. He earned his Ph.D. in Organic Chemistry from the Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, and conducted postdoctoral research at the Scripps Research Institute in the United States. Currently, his research group focuses on: total synthesis of medicinal natural products and functional materials driven by synthetic methodology innovation; high-end instrument development, synthesis automation, and intelligence guided by scientific nature modeling; with a particular focus on photo/electrocatalytic activation of chemical bonds and their industrial applications.Dominik MunzHigh Resolution ImageDownload MS PowerPoint SlideDominik Munz (Ph.D. 2013) is Professor for Coordination Chemistry at Saarland University, Germany. Research in the group targets zwitterionic organometallics and diradicals with a specific interest for bond activation chemistry, catalysis, mechanisms, spectroscopic properties and─of course─their photophysics.ReferencesClick to copy section linkSection link copied! This article references 4 other publications. 1Bitterwolf, T. E. Organometallic photochemistry at the end of its first century. J. Organomet. Chem. 2004, 689 (24), 3939– 3952, DOI: 10.1016/j.jorganchem.2004.06.023 Google ScholarThere is no corresponding record for this reference.2Dedeian, K.; Djurovich, P. I.; Garces, F. O.; Carlson, G.; Watts, R. J. A new synthetic route to the preparation of a series of strong photoreducing agents: fac-tris-ortho-metalated complexes of iridium(III) with substituted 2-phenylpyridines. Inorg. Chem. 1991, 30 (8), 1685– 1687, DOI: 10.1021/ic00008a003 Google Scholar2A new synthetic route to the preparation of a series of strong photoreducing agents: fac-tris-ortho-metalated complexes of iridium(III) with substituted 2-phenylpyridinesDedeian, K.; Djurovich, P. I.; Garces, F. O.; Carlson, G.; Watts, R. J.Inorganic Chemistry (1991), 30 (8), 1685-7CODEN: INOCAJ; ISSN:0020-1669. Reaction of 2-phenylpyridine (Hppy) with Ir(acac)3 (acac = acetylacetonato) in refluxing glycerol gives the fac-tris-ortho-metalate of Ir(III), fac-Ir(ppy)3 in high yield (45%). Phenyl-ring-substituted derivs. of 2-phenylpyridine (R-Hppy) were prepd. by cross-coupling of 2-bromopyridine with substituted bromobenzenes. These react with Ir(acac)3 in a manner analogous to Hppy to give similarly high yields (40-75%) of their resp. tris-ortho-metalates, fac-Ir(R-ppy)3. >> More from SciFinder ®https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK3MXhvVGks7s%253D&md5=b4d527ac1157cd2a04a34ccb536847673Lamansky, S.; Djurovich, P.; Murphy, D.; Abdel-Razzaq, F.; Kwong, R.; Tsyba, I.; Bortz, M.; Mui, B.; Bau, R.; Thompson, M. E. Synthesis and Characterization of Phosphorescent Cyclometalated Iridium Complexes. Inorg. Chem. 2001, 40 (7), 1704– 1711, DOI: 10.1021/ic0008969 Google Scholar3Synthesis and Characterization of Phosphorescent Cyclometalated Iridium ComplexesLamansky, Sergey; Djurovich, Peter; Murphy, Drew; Abdel-Razzaq, Feras; Kwong, Raymond; Tsyba, Irina; Bortz, Manfred; Mui, Becky; Bau, Robert; Thompson, Mark E.Inorganic Chemistry (2001), 40 (7), 1704-1711CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society) The prepn., photophysics, and solid state structures of octahedral organometallic Ir complexes with several different cyclometalated ligands are reported. IrCl3·nH2O cleanly cyclometalates a no. of different compds. (i.e., 2-phenylpyridine (ppy), 2-(p-tolyl)pyridine (tpy), benzoquinoline (bzq), 2-phenylbenzothiazole (bt), 2-(1-naphthyl)benzothiazole (bsn), and 2-phenylquinoline (pq)), forming the corresponding chloride-bridged dimers, C-N2Ir(μ-Cl)2IrC-N2 (C-N is a cyclometalated ligand) in good yield. These chloride-bridged dimers react with acetyl acetone (acacH) and other bidentate, monoanionic ligands such as picolinic acid (picH) and N-methylsalicylimine (salH), to give monomeric C-N2Ir(LX) complexes (LX = acac, pic, sal). The emission spectra of these complexes are largely governed by the nature of the cyclometalating ligand, leading to λmax values from 510 to 606 nm for the complexes reported here. The strong spin-orbit coupling of iridium mixes the formally forbidden 3MLCT and 3π-π* transitions with the allowed 1MLCT, leading to a strong phosphorescence with good quantum efficiencies (0.1-0.4) and room temp. lifetimes in the microsecond regime. The emission spectra of the C-N2Ir(LX) complexes are surprisingly similar to the fac-IrC-N3 complex of the same ligand, even though the structures of the two complexes are markedly different. The crystal structures of two of the C-N2Ir(acac) complexes (i.e., C-N = ppy and tpy) have been detd. Both complexes show cis-C,C', trans-N,N' disposition of the two cyclometalated ligands, similar to the structures reported for other complexes with a "C-N2Ir" fragment. NMR data (1H and 13C) support a similar structure for all of the C-N2Ir(LX) complexes. Close intermol. contacts in both (ppy)2Ir(acac) and (tpy)2Ir(acac) lead to significantly red shifted emission spectra for cryst. samples of the ppy and tpy complexes relative to their soln. spectra. >> More from SciFinder ®https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3MXhsVGnurc%253D&md5=4374fc8305b2d0a7dcb21baa50fdfd284Förster, C.; Heinze, K. Photophysics and photochemistry with Earth-abundant metals – fundamentals and concepts. Chem. Soc. Rev. 2020, 49 (4), 1057– 1070, DOI: 10.1039/C9CS00573K Google Scholar4Photophysics and photochemistry with Earth-abundant metals - fundamentals and conceptsForster Christoph; Heinze KatjaChemical Society reviews (2020), 49 (4), 1057-1070 ISSN:. Recent exciting developments in the area of mononuclear photoactive complexes with Earth-abundant metal ions (Cu, Zr, Fe, Cr) for potential eco-friendly applications in (phosphorescent) organic light emitting diodes, in imaging and sensing systems, in dye-sensitized solar cells and as photocatalysts are presented. Challenges, in particular the extension of excited state lifetimes, and recent conceptual breakthroughs in substituting precious and rare-Earth metal ions (e.g. Ru, Ir, Pt, Au, Eu) in these applications by abundant ions are outlined with selected examples. Relevant fundamentals of photophysics and photochemistry are discussed first, followed by conceptual and instructive case studies. >> More from SciFinder ®https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BB38%252FovVOmuw%253D%253D&md5=f7e2ce8d8cba092815fd5c69fa557ee8Wenger, O. S. Photoactive Complexes with Earth-Abundant Metals. J. Am. Chem. Soc. 2018, 140 (42), 13522– 13533, DOI: 10.1021/jacs.8b08822 Google Scholar4Photoactive Complexes with Earth-Abundant MetalsWenger, Oliver S.Journal of the American Chemical Society (2018), 140 (42), 13522-13533CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society) A review. In this invited Perspective, recent developments and possible future directions of research on photoactive coordination compds. made from nonprecious transition metal elements will be discussed. The focus is on conceptually new, structurally well-characterized complexes with excited-state lifetimes between 10 ps and 1 ms in fluid soln. for possible applications in photosensitizing, light-harvesting, luminescence and catalysis. The key metal elements considered herein are Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, W and Ce in various oxidn. states equipped with diverse ligands, giving access to long-lived excited states via a range of fundamentally different types of electronic transitions. Research performed in this area over the past five years demonstrated that a much broader spectrum of metal complexes than what was long considered relevant exhibits useful photophysics and photochem. >> More from SciFinder ®https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhvVygtrnE&md5=942e66e35a4713968f4411e2ea17ebcfCited By Click to copy section linkSection link copied!This article has not yet been cited by other publications.Download PDFFiguresReferencesOpen PDF Get e-AlertsGet e-AlertsOrganometallicsCite this: Organometallics 2024, 43, 16, 1659–1661Click to copy citationCitation copied!https://doi.org/10.1021/acs.organomet.4c00309Published August 26, 2024 Publication History Received 9 July 2024Published online 26 August 2024Published in issue 26 August 2024Copyright © Published 2024 by American Chemical Society. This publication is available under these Terms of Use. Request reuse permissionsArticle Views-Altmetric-Citations-Learn about these metrics closeArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated.Recommended Articles FiguresReferencesDebashis AdhikariHigh Resolution ImageDownload MS PowerPoint SlideDebashis Adhikari is currently an associate professor of Chemistry in IISER Mohali, India. He earned his Ph.D. in inorganic chemistry from Indiana University, Bloomington, and performed postdoctoral research in Northwestern University, Evanston. His group focuses on redox-active ligands applied towards homogeneous catalysis, borrowing hydrogen reactions, and making strong photo-oxidants and reductants under visible light.Sun DongbangHigh Resolution ImageDownload MS PowerPoint SlideSun Dongbang (Ph.D. 2020) is an assistant professor in the Department of Chemistry at Sogang University, South Korea. Her Ph.D. and postdoctoral studies have centered around total synthesis of natural products and methodology development using transition metals to construct structurally complex motifs. The current group's research interests lie in the development of new transition-metal catalysis using earth-abundant metals and photoredox-catalyzed synthetic methods.Xuefeng JiangHigh Resolution ImageDownload MS PowerPoint SlideXuefeng Jiang (Ph.D. 2008) is a Professor for Organic Chemistry at East China Normal University, China. He earned his Ph.D. in Organic Chemistry from the Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, and conducted postdoctoral research at the Scripps Research Institute in the United States. Currently, his research group focuses on: total synthesis of medicinal natural products and functional materials driven by synthetic methodology innovation; high-end instrument development, synthesis automation, and intelligence guided by scientific nature modeling; with a particular focus on photo/electrocatalytic activation of chemical bonds and their industrial applications.Dominik MunzHigh Resolution ImageDownload MS PowerPoint SlideDominik Munz (Ph.D. 2013) is Professor for Coordination Chemistry at Saarland University, Germany. Research in the group targets zwitterionic organometallics and diradicals with a specific interest for bond activation chemistry, catalysis, mechanisms, spectroscopic properties and─of course─their photophysics.References This article references 4 other publications. 1Bitterwolf, T. E. Organometallic photochemistry at the end of its first century. J. Organomet. Chem. 2004, 689 (24), 3939– 3952, DOI: 10.1016/j.jorganchem.2004.06.023 There is no corresponding record for this reference.2Dedeian, K.; Djurovich, P. I.; Garces, F. O.; Carlson, G.; Watts, R. J. A new synthetic route to the preparation of a series of strong photoreducing agents: fac-tris-ortho-metalated complexes of iridium(III) with substituted 2-phenylpyridines. Inorg. Chem. 1991, 30 (8), 1685– 1687, DOI: 10.1021/ic00008a003 2A new synthetic route to the preparation of a series of strong photoreducing agents: fac-tris-ortho-metalated complexes of iridium(III) with substituted 2-phenylpyridinesDedeian, K.; Djurovich, P. I.; Garces, F. O.; Carlson, G.; Watts, R. J.Inorganic Chemistry (1991), 30 (8), 1685-7CODEN: INOCAJ; ISSN:0020-1669. Reaction of 2-phenylpyridine (Hppy) with Ir(acac)3 (acac = acetylacetonato) in refluxing glycerol gives the fac-tris-ortho-metalate of Ir(III), fac-Ir(ppy)3 in high yield (45%). Phenyl-ring-substituted derivs. of 2-phenylpyridine (R-Hppy) were prepd. by cross-coupling of 2-bromopyridine with substituted bromobenzenes. These react with Ir(acac)3 in a manner analogous to Hppy to give similarly high yields (40-75%) of their resp. tris-ortho-metalates, fac-Ir(R-ppy)3. >> More from SciFinder ®https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK3MXhvVGks7s%253D&md5=b4d527ac1157cd2a04a34ccb536847673Lamansky, S.; Djurovich, P.; Murphy, D.; Abdel-Razzaq, F.; Kwong, R.; Tsyba, I.; Bortz, M.; Mui, B.; Bau, R.; Thompson, M. E. Synthesis and Characterization of Phosphorescent Cyclometalated Iridium Complexes. Inorg. Chem. 2001, 40 (7), 1704– 1711, DOI: 10.1021/ic0008969 3Synthesis and Characterization of Phosphorescent Cyclometalated Iridium ComplexesLamansky, Sergey; Djurovich, Peter; Murphy, Drew; Abdel-Razzaq, Feras; Kwong, Raymond; Tsyba, Irina; Bortz, Manfred; Mui, Becky; Bau, Robert; Thompson, Mark E.Inorganic Chemistry (2001), 40 (7), 1704-1711CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society) The prepn., photophysics, and solid state structures of octahedral organometallic Ir complexes with several different cyclometalated ligands are reported. IrCl3·nH2O cleanly cyclometalates a no. of different compds. (i.e., 2-phenylpyridine (ppy), 2-(p-tolyl)pyridine (tpy), benzoquinoline (bzq), 2-phenylbenzothiazole (bt), 2-(1-naphthyl)benzothiazole (bsn), and 2-phenylquinoline (pq)), forming the corresponding chloride-bridged dimers, C-N2Ir(μ-Cl)2IrC-N2 (C-N is a cyclometalated ligand) in good yield. These chloride-bridged dimers react with acetyl acetone (acacH) and other bidentate, monoanionic ligands such as picolinic acid (picH) and N-methylsalicylimine (salH), to give monomeric C-N2Ir(LX) complexes (LX = acac, pic, sal). The emission spectra of these complexes are largely governed by the nature of the cyclometalating ligand, leading to λmax values from 510 to 606 nm for the complexes reported here. The strong spin-orbit coupling of iridium mixes the formally forbidden 3MLCT and 3π-π* transitions with the allowed 1MLCT, leading to a strong phosphorescence with good quantum efficiencies (0.1-0.4) and room temp. lifetimes in the microsecond regime. The emission spectra of the C-N2Ir(LX) complexes are surprisingly similar to the fac-IrC-N3 complex of the same ligand, even though the structures of the two complexes are markedly different. The crystal structures of two of the C-N2Ir(acac) complexes (i.e., C-N = ppy and tpy) have been detd. Both complexes show cis-C,C', trans-N,N' disposition of the two cyclometalated ligands, similar to the structures reported for other complexes with a "C-N2Ir" fragment. NMR data (1H and 13C) support a similar structure for all of the C-N2Ir(LX) complexes. Close intermol. contacts in both (ppy)2Ir(acac) and (tpy)2Ir(acac) lead to significantly red shifted emission spectra for cryst. samples of the ppy and tpy complexes relative to their soln. spectra. >> More from SciFinder ®https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3MXhsVGnurc%253D&md5=4374fc8305b2d0a7dcb21baa50fdfd284Förster, C.; Heinze, K. Photophysics and photochemistry with Earth-abundant metals – fundamentals and concepts. Chem. Soc. Rev. 2020, 49 (4), 1057– 1070, DOI: 10.1039/C9CS00573K 4Photophysics and photochemistry with Earth-abundant metals - fundamentals and conceptsForster Christoph; Heinze KatjaChemical Society reviews (2020), 49 (4), 1057-1070 ISSN:. Recent exciting developments in the area of mononuclear photoactive complexes with Earth-abundant metal ions (Cu, Zr, Fe, Cr) for potential eco-friendly applications in (phosphorescent) organic light emitting diodes, in imaging and sensing systems, in dye-sensitized solar cells and as photocatalysts are presented. Challenges, in particular the extension of excited state lifetimes, and recent conceptual breakthroughs in substituting precious and rare-Earth metal ions (e.g. Ru, Ir, Pt, Au, Eu) in these applications by abundant ions are outlined with selected examples. Relevant fundamentals of photophysics and photochemistry are discussed first, followed by conceptual and instructive case studies. >> More from SciFinder ®https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BB38%252FovVOmuw%253D%253D&md5=f7e2ce8d8cba092815fd5c69fa557ee8Wenger, O. S. Photoactive Complexes with Earth-Abundant Metals. J. Am. Chem. Soc. 2018, 140 (42), 13522– 13533, DOI: 10.1021/jacs.8b08822 4Photoactive Complexes with Earth-Abundant MetalsWenger, Oliver S.Journal of the American Chemical Society (2018), 140 (42), 13522-13533CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society) A review. In this invited Perspective, recent developments and possible future directions of research on photoactive coordination compds. made from nonprecious transition metal elements will be discussed. The focus is on conceptually new, structurally well-characterized complexes with excited-state lifetimes between 10 ps and 1 ms in fluid soln. for possible applications in photosensitizing, light-harvesting, luminescence and catalysis. The key metal elements considered herein are Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, W and Ce in various oxidn. states equipped with diverse ligands, giving access to long-lived excited states via a range of fundamentally different types of electronic transitions. Research performed in this area over the past five years demonstrated that a much broader spectrum of metal complexes than what was long considered relevant exhibits useful photophysics and photochem. >> More from SciFinder ®https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhvVygtrnE&md5=942e66e35a4713968f4411e2ea17ebcf
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