Square-Planar Heteroleptic Complexes of α-Diimine-Ni<sup>II</sup>-Catecholate Type: Intramolecular Ligand-to-Ligand Charge Transfer
Two heteroleptic Ni<sup>II</sup> complexes combined the redox-active catecholate and 2,2′- bipyridine ligand platforms were synthesized to observe a photoinduced intramolecular ligand-to-ligand charge transfer (LL’CT, HOMO<sub>catecholate</sub> → LUMO<sub>α-diimine</...
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MDPI AG
2021-07-01
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| author | Kira I. Pashanova Vladlena O. Bitkina Ilya A. Yakushev Maxim V. Arsenyev Alexandr V. Piskunov |
| author_facet | Kira I. Pashanova Vladlena O. Bitkina Ilya A. Yakushev Maxim V. Arsenyev Alexandr V. Piskunov |
| author_sort | Kira I. Pashanova |
| collection | DOAJ |
| description | Two heteroleptic Ni<sup>II</sup> complexes combined the redox-active catecholate and 2,2′- bipyridine ligand platforms were synthesized to observe a photoinduced intramolecular ligand-to-ligand charge transfer (LL’CT, HOMO<sub>catecholate</sub> → LUMO<sub>α-diimine</sub>). A molecular design of compound [Ni<sup>II</sup>(3,6-Cat)(bipy)]∙CH<sub>3</sub>CN (<b>1</b>) on the base of bulky 3,6-di-<i>tert</i>-butyl-<i>o</i>-benzoquinone (<b>3,6-DTBQ</b>) was an annelation of the ligand with an electron donor glycol fragment, producing derivative [Ni<sup>II</sup>(3,6-Cat<sup>gly</sup>)(bipy)]∙CH<sub>2</sub>Cl<sub>2</sub> (<b>2</b>), in order to influence the energy of LL’CT transition. A substantial longwave shift of the absorption peak was observed in the UV-Vis-NIR spectra of <b>2</b> compared with those in <b>1</b>. In addition, the studied Ni<sup>II</sup> derivatives demonstrated a pronounced negative solvatochromism, which was established using a broad set of solvents. The molecular geometry of both compounds can be ascribed as an insignificantly distorted square-planar type, and the π–π intermolecular stacking of the neighboring α-diimines is realized in a crystal packing. There is a lamellar crystal structure for complex <b>1</b>, whereas the perpendicular T-motifs with the inter-stacks attractive π–π interactions form the packing of complex <b>2</b>. The redox-active nature of ligand systems was clearly shown through the electrochemical study: a quasi-reversible one-electron reduction of 2,2′-bipyridine and two reversible successive one-electron oxidative conversations (“catecholate dianion—<i>o</i>-benzosemiquinonato radical anion—neutral <i>o</i>-benzoquinone”) were detected. |
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| institution | Directory Open Access Journal |
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| spelling | doaj.art-c68b6d9d42a84fdab815718aa5b684cd2023-11-22T06:00:50ZengMDPI AGMolecules1420-30492021-07-012615462210.3390/molecules26154622Square-Planar Heteroleptic Complexes of α-Diimine-Ni<sup>II</sup>-Catecholate Type: Intramolecular Ligand-to-Ligand Charge TransferKira I. Pashanova0Vladlena O. Bitkina1Ilya A. Yakushev2Maxim V. Arsenyev3Alexandr V. Piskunov4Laboratory of Metal Complexes with Redox-Active Ligands, G.A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences, 49 Tropinina Street, 603137 Nizhny Novgorod, RussiaLaboratory of Metal Complexes with Redox-Active Ligands, G.A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences, 49 Tropinina Street, 603137 Nizhny Novgorod, RussiaN.S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, 31 Leninski Prospect, 119991 Moscow, RussiaLaboratory of Metal Complexes with Redox-Active Ligands, G.A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences, 49 Tropinina Street, 603137 Nizhny Novgorod, RussiaN.S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, 31 Leninski Prospect, 119991 Moscow, RussiaTwo heteroleptic Ni<sup>II</sup> complexes combined the redox-active catecholate and 2,2′- bipyridine ligand platforms were synthesized to observe a photoinduced intramolecular ligand-to-ligand charge transfer (LL’CT, HOMO<sub>catecholate</sub> → LUMO<sub>α-diimine</sub>). A molecular design of compound [Ni<sup>II</sup>(3,6-Cat)(bipy)]∙CH<sub>3</sub>CN (<b>1</b>) on the base of bulky 3,6-di-<i>tert</i>-butyl-<i>o</i>-benzoquinone (<b>3,6-DTBQ</b>) was an annelation of the ligand with an electron donor glycol fragment, producing derivative [Ni<sup>II</sup>(3,6-Cat<sup>gly</sup>)(bipy)]∙CH<sub>2</sub>Cl<sub>2</sub> (<b>2</b>), in order to influence the energy of LL’CT transition. A substantial longwave shift of the absorption peak was observed in the UV-Vis-NIR spectra of <b>2</b> compared with those in <b>1</b>. In addition, the studied Ni<sup>II</sup> derivatives demonstrated a pronounced negative solvatochromism, which was established using a broad set of solvents. The molecular geometry of both compounds can be ascribed as an insignificantly distorted square-planar type, and the π–π intermolecular stacking of the neighboring α-diimines is realized in a crystal packing. There is a lamellar crystal structure for complex <b>1</b>, whereas the perpendicular T-motifs with the inter-stacks attractive π–π interactions form the packing of complex <b>2</b>. The redox-active nature of ligand systems was clearly shown through the electrochemical study: a quasi-reversible one-electron reduction of 2,2′-bipyridine and two reversible successive one-electron oxidative conversations (“catecholate dianion—<i>o</i>-benzosemiquinonato radical anion—neutral <i>o</i>-benzoquinone”) were detected.https://www.mdpi.com/1420-3049/26/15/4622<i>o</i>-benzoquinoneα-diimineNi<sup>II</sup> ionphotoinduced intramolecular charge transferπ–π stackingSC X-ray |
| spellingShingle | Kira I. Pashanova Vladlena O. Bitkina Ilya A. Yakushev Maxim V. Arsenyev Alexandr V. Piskunov Square-Planar Heteroleptic Complexes of α-Diimine-Ni<sup>II</sup>-Catecholate Type: Intramolecular Ligand-to-Ligand Charge Transfer Molecules <i>o</i>-benzoquinone α-diimine Ni<sup>II</sup> ion photoinduced intramolecular charge transfer π–π stacking SC X-ray |
| title | Square-Planar Heteroleptic Complexes of α-Diimine-Ni<sup>II</sup>-Catecholate Type: Intramolecular Ligand-to-Ligand Charge Transfer |
| title_full | Square-Planar Heteroleptic Complexes of α-Diimine-Ni<sup>II</sup>-Catecholate Type: Intramolecular Ligand-to-Ligand Charge Transfer |
| title_fullStr | Square-Planar Heteroleptic Complexes of α-Diimine-Ni<sup>II</sup>-Catecholate Type: Intramolecular Ligand-to-Ligand Charge Transfer |
| title_full_unstemmed | Square-Planar Heteroleptic Complexes of α-Diimine-Ni<sup>II</sup>-Catecholate Type: Intramolecular Ligand-to-Ligand Charge Transfer |
| title_short | Square-Planar Heteroleptic Complexes of α-Diimine-Ni<sup>II</sup>-Catecholate Type: Intramolecular Ligand-to-Ligand Charge Transfer |
| title_sort | square planar heteroleptic complexes of α diimine ni sup ii sup catecholate type intramolecular ligand to ligand charge transfer |
| topic | <i>o</i>-benzoquinone α-diimine Ni<sup>II</sup> ion photoinduced intramolecular charge transfer π–π stacking SC X-ray |
| url | https://www.mdpi.com/1420-3049/26/15/4622 |
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