{"title":"Fluorescence Emission Modulation of Alkynyl-Functionalized Iron(II) Spin-Crossover Complexes","authors":"Yang Qu, Rong Sun, Bing-Wu Wang, Song Gao","doi":"10.31635/ccschem.024.202404670","DOIUrl":null,"url":null,"abstract":"<p>Combining spin crossover (SCO) and fluorescence properties could respond to multiple physical stimulus and is meaningful for the development of switches and imaging tools. In this work, we present a new family of neutral mononuclear iron(II) complexes, denoted as Fe(<b xmlns:bkstg=\"http://www.atypon.com/backstage-ns\" xmlns:fn=\"http://www.w3.org/2005/xpath-functions\" xmlns:pxje=\"java:com.atypon.frontend.services.impl.PassportXslJavaExtentions\" xmlns:urlutil=\"java:com.atypon.literatum.customization.UrlUtil\" xmlns:xlink=\"http://www.w3.org/1999/xlink\">\n<bold>L</bold></b><sup>1–3</sup>)<sub>2</sub> and Fe(<b xmlns:bkstg=\"http://www.atypon.com/backstage-ns\" xmlns:fn=\"http://www.w3.org/2005/xpath-functions\" xmlns:pxje=\"java:com.atypon.frontend.services.impl.PassportXslJavaExtentions\" xmlns:urlutil=\"java:com.atypon.literatum.customization.UrlUtil\" xmlns:xlink=\"http://www.w3.org/1999/xlink\">\n<bold>L</bold></b><sup>3</sup>)<sub>2</sub>·CH<sub>2</sub>Cl<sub>2</sub> with N<sub>4</sub>O<sub>2</sub> donor sets. These complexes were synthesized employing a series of tridentate Schiff base ligands, which contain an ethynyl group (H<b xmlns:bkstg=\"http://www.atypon.com/backstage-ns\" xmlns:fn=\"http://www.w3.org/2005/xpath-functions\" xmlns:pxje=\"java:com.atypon.frontend.services.impl.PassportXslJavaExtentions\" xmlns:urlutil=\"java:com.atypon.literatum.customization.UrlUtil\" xmlns:xlink=\"http://www.w3.org/1999/xlink\">\n<bold>L</bold></b><sup>1–3</sup> = 3-ethynyl-<i>N</i>′-((4-methylpyridin-2-yl)methylene)benzohydrazide (<b xmlns:bkstg=\"http://www.atypon.com/backstage-ns\" xmlns:fn=\"http://www.w3.org/2005/xpath-functions\" xmlns:pxje=\"java:com.atypon.frontend.services.impl.PassportXslJavaExtentions\" xmlns:urlutil=\"java:com.atypon.literatum.customization.UrlUtil\" xmlns:xlink=\"http://www.w3.org/1999/xlink\">\n<bold>4MePAH-3EyBHZ</bold></b>, H<b xmlns:bkstg=\"http://www.atypon.com/backstage-ns\" xmlns:fn=\"http://www.w3.org/2005/xpath-functions\" xmlns:pxje=\"java:com.atypon.frontend.services.impl.PassportXslJavaExtentions\" xmlns:urlutil=\"java:com.atypon.literatum.customization.UrlUtil\" xmlns:xlink=\"http://www.w3.org/1999/xlink\">\n<bold>L</bold></b><sup>1</sup>), 3-ethynyl-<i>N</i>′-((4-methoxylpyridin-2-yl)methylene)benzohydrazide (<b xmlns:bkstg=\"http://www.atypon.com/backstage-ns\" xmlns:fn=\"http://www.w3.org/2005/xpath-functions\" xmlns:pxje=\"java:com.atypon.frontend.services.impl.PassportXslJavaExtentions\" xmlns:urlutil=\"java:com.atypon.literatum.customization.UrlUtil\" xmlns:xlink=\"http://www.w3.org/1999/xlink\">\n<bold>4OMePAH-3EyBHZ</bold></b>, H<b xmlns:bkstg=\"http://www.atypon.com/backstage-ns\" xmlns:fn=\"http://www.w3.org/2005/xpath-functions\" xmlns:pxje=\"java:com.atypon.frontend.services.impl.PassportXslJavaExtentions\" xmlns:urlutil=\"java:com.atypon.literatum.customization.UrlUtil\" xmlns:xlink=\"http://www.w3.org/1999/xlink\">\n<bold>L</bold></b><sup>2</sup>), 3-ethynyl-<i>N</i>′-((5-methylpyridin-2-yl)methylene)benzohydrazide (<b xmlns:bkstg=\"http://www.atypon.com/backstage-ns\" xmlns:fn=\"http://www.w3.org/2005/xpath-functions\" xmlns:pxje=\"java:com.atypon.frontend.services.impl.PassportXslJavaExtentions\" xmlns:urlutil=\"java:com.atypon.literatum.customization.UrlUtil\" xmlns:xlink=\"http://www.w3.org/1999/xlink\">\n<bold>5MePAH-3EyBHZ</bold></b>, H<b xmlns:bkstg=\"http://www.atypon.com/backstage-ns\" xmlns:fn=\"http://www.w3.org/2005/xpath-functions\" xmlns:pxje=\"java:com.atypon.frontend.services.impl.PassportXslJavaExtentions\" xmlns:urlutil=\"java:com.atypon.literatum.customization.UrlUtil\" xmlns:xlink=\"http://www.w3.org/1999/xlink\">\n<bold>L</bold></b><sup>3</sup>)). Variable-temperature magnetic susceptibility measurements revealed that Fe(<b xmlns:bkstg=\"http://www.atypon.com/backstage-ns\" xmlns:fn=\"http://www.w3.org/2005/xpath-functions\" xmlns:pxje=\"java:com.atypon.frontend.services.impl.PassportXslJavaExtentions\" xmlns:urlutil=\"java:com.atypon.literatum.customization.UrlUtil\" xmlns:xlink=\"http://www.w3.org/1999/xlink\">\n<bold>L</bold></b><sup>1</sup>)<sub>2</sub> exhibits an abrupt and complete SCO with characteristic temperature <i>T</i><sub>1/2↓</sub> = 176 K and <i>T</i><sub>1/2↑</sub> = 178 K; Fe(<b xmlns:bkstg=\"http://www.atypon.com/backstage-ns\" xmlns:fn=\"http://www.w3.org/2005/xpath-functions\" xmlns:pxje=\"java:com.atypon.frontend.services.impl.PassportXslJavaExtentions\" xmlns:urlutil=\"java:com.atypon.literatum.customization.UrlUtil\" xmlns:xlink=\"http://www.w3.org/1999/xlink\">\n<bold>L</bold></b><sup>2</sup>)<sub>2</sub> exhibits an abrupt and complete SCO with <i>T</i><sub>1/2↓</sub> = 214 K and <i>T</i><sub>1/2↑</sub> = 219 K; Fe(<b xmlns:bkstg=\"http://www.atypon.com/backstage-ns\" xmlns:fn=\"http://www.w3.org/2005/xpath-functions\" xmlns:pxje=\"java:com.atypon.frontend.services.impl.PassportXslJavaExtentions\" xmlns:urlutil=\"java:com.atypon.literatum.customization.UrlUtil\" xmlns:xlink=\"http://www.w3.org/1999/xlink\">\n<bold>L</bold></b><sup>3</sup>)<sub>2</sub> exhibits an abrupt and complete SCO with <i>T</i><sub>1/2↓</sub> = 218 K and<i> T</i><sub>1/2↑</sub> = 226 K. The partial conformational inversion is observed between the high spin and low spin state of Fe(<b xmlns:bkstg=\"http://www.atypon.com/backstage-ns\" xmlns:fn=\"http://www.w3.org/2005/xpath-functions\" xmlns:pxje=\"java:com.atypon.frontend.services.impl.PassportXslJavaExtentions\" xmlns:urlutil=\"java:com.atypon.literatum.customization.UrlUtil\" xmlns:xlink=\"http://www.w3.org/1999/xlink\">\n<bold>L</bold></b><sup>2</sup>)<sub>2</sub> evidenced by the variable-temperature single-crystal X-ray diffraction analysis. An unusual increase of emission intensity was observed in the fluorescence spectra of Fe(<b xmlns:bkstg=\"http://www.atypon.com/backstage-ns\" xmlns:fn=\"http://www.w3.org/2005/xpath-functions\" xmlns:pxje=\"java:com.atypon.frontend.services.impl.PassportXslJavaExtentions\" xmlns:urlutil=\"java:com.atypon.literatum.customization.UrlUtil\" xmlns:xlink=\"http://www.w3.org/1999/xlink\">\n<bold>L</bold></b><sup>1</sup>)<sub>2</sub> and Fe(<b xmlns:bkstg=\"http://www.atypon.com/backstage-ns\" xmlns:fn=\"http://www.w3.org/2005/xpath-functions\" xmlns:pxje=\"java:com.atypon.frontend.services.impl.PassportXslJavaExtentions\" xmlns:urlutil=\"java:com.atypon.literatum.customization.UrlUtil\" xmlns:xlink=\"http://www.w3.org/1999/xlink\">\n<bold>L</bold></b><sup>2</sup>)<sub>2</sub> during the heating SCO process. These findings are both valuable in the study of spin-fluorescence interaction and synthesis of new multifunctional SCO complexes.</p>","PeriodicalId":9810,"journal":{"name":"CCS Chemistry","volume":null,"pages":null},"PeriodicalIF":9.4000,"publicationDate":"2024-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"CCS Chemistry","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.31635/ccschem.024.202404670","RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"CHEMISTRY, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
Combining spin crossover (SCO) and fluorescence properties could respond to multiple physical stimulus and is meaningful for the development of switches and imaging tools. In this work, we present a new family of neutral mononuclear iron(II) complexes, denoted as Fe(L1–3)2 and Fe(L3)2·CH2Cl2 with N4O2 donor sets. These complexes were synthesized employing a series of tridentate Schiff base ligands, which contain an ethynyl group (HL1–3 = 3-ethynyl-N′-((4-methylpyridin-2-yl)methylene)benzohydrazide (4MePAH-3EyBHZ, HL1), 3-ethynyl-N′-((4-methoxylpyridin-2-yl)methylene)benzohydrazide (4OMePAH-3EyBHZ, HL2), 3-ethynyl-N′-((5-methylpyridin-2-yl)methylene)benzohydrazide (5MePAH-3EyBHZ, HL3)). Variable-temperature magnetic susceptibility measurements revealed that Fe(L1)2 exhibits an abrupt and complete SCO with characteristic temperature T1/2↓ = 176 K and T1/2↑ = 178 K; Fe(L2)2 exhibits an abrupt and complete SCO with T1/2↓ = 214 K and T1/2↑ = 219 K; Fe(L3)2 exhibits an abrupt and complete SCO with T1/2↓ = 218 K and T1/2↑ = 226 K. The partial conformational inversion is observed between the high spin and low spin state of Fe(L2)2 evidenced by the variable-temperature single-crystal X-ray diffraction analysis. An unusual increase of emission intensity was observed in the fluorescence spectra of Fe(L1)2 and Fe(L2)2 during the heating SCO process. These findings are both valuable in the study of spin-fluorescence interaction and synthesis of new multifunctional SCO complexes.
期刊介绍：
CCS Chemistry, the flagship publication of the Chinese Chemical Society, stands as a leading international chemistry journal based in China. With a commitment to global outreach in both contributions and readership, the journal operates on a fully Open Access model, eliminating subscription fees for contributing authors. Issued monthly, all articles are published online promptly upon reaching final publishable form. Additionally, authors have the option to expedite the posting process through Immediate Online Accepted Article posting, making a PDF of their accepted article available online upon journal acceptance.
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