Platinum(IV) Complexes with Tridentate, NNC-Coordinating Ligands: Synthesis, Structures, and Luminescence
Platinum(II) complexes of NNC-cyclometalating ligands based on 6-phenyl-2,2′-bipyridine (HL1) have been widely investigated for their luminescence properties. We describe how PtL1Cl and five analogues with differently substituted aryl rings, PtL2–6Cl, can be oxidized with chlorine and/or iodobenzen...
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| Published in: | Inorganic chemistry Vol. 62; no. 4; pp. 1306 - 1322 |
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| Main Authors: | , , |
| Format: | Journal Article |
| Language: | English |
| Published: |
United States
American Chemical Society
30-01-2023
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| Online Access: | Get full text |
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| Summary: | Platinum(II) complexes of NNC-cyclometalating ligands based on 6-phenyl-2,2′-bipyridine (HL1) have been widely investigated for their luminescence properties. We describe how PtL1Cl and five analogues with differently substituted aryl rings, PtL2–6Cl, can be oxidized with chlorine and/or iodobenzene dichloride to generate Pt(IV) compounds of the form Pt(NNC-L n )Cl3 (n = 1–6). The molecular structures of several of them have been determined by X-ray diffraction. These PtL n Cl3 compounds react with 2-arylpyridines to give a new class of Pt(IV) complex of the form [Pt(NNC)(NC)Cl]+. Elevated temperatures are required, and the reaction is accompanied by competitive reduction processes and generation of side-products; however, four examples of such complexes have been isolated and their molecular structures determined. Reaction of PtL1Cl3 with HL1 similarly generates [Pt(NNC-L1)2]2+, which we believe to be the first example of a bis-tridentate Pt(IV) complex. The lowest-energy bands in the UV–vis absorption spectra of all the PtL n Cl3 compounds are displaced to higher energy relative to the Pt(II) precursors, but they red-shift with the electron richness of the aryl ring, consistent with predominantly 1[πAr → π*NN] character to the pertinent excited state. A similar trend is observed for the [Pt(NNC)(NC)Cl]+ complexes. They display phosphorescence in solution at room temperature, centered around 500 nm for [PtL1(ppy)Cl]+ and [Pt(L1)2]2+, and 550 nm for methoxy-substituted derivatives. The lifetimes are in the microsecond range, rising to hundreds of microseconds at 77 K, consistent with triplet excited states of primarily 3[πAr → π*NN] character with relatively little participation of the metal. |
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| Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
| ISSN: | 0020-1669 1520-510X |
| DOI: | 10.1021/acs.inorgchem.2c04116 |