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Substituted 4,4′-Stilbenoid NCN-Pincer Platinum(II) Complexes. Luminescence and Tuning of the Electronic and NLO Properties and the Application in an OLED
A series of 4,4′-disubstituted organic−organometallic stilbenes, i.e., the 4′-substituted stilbenoid-NCN-pincer platinum(II) complexes [PtCl(NCN-R-4)] (NCN-R-4 = [C6H2(CH2NMe2)2-2,6-R-4]− in which R = C2H2C6H4-R′-4′ with R′ = NPh2, NMe2, OMe, SiMe3 H, I, CN, NO2) (1−8), were studied for their electr...
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| Published in: | Organometallics 2008-04, Vol.27 (8), p.1690-1701 |
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| Main Authors: | , , , , , , , , , , , , , |
| Format: | Article |
| Language: | English |
| Citations: | Items that this one cites Items that cite this one |
| Online Access: | Get full text |
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| Summary: | A series of 4,4′-disubstituted organic−organometallic stilbenes, i.e., the 4′-substituted stilbenoid-NCN-pincer platinum(II) complexes [PtCl(NCN-R-4)] (NCN-R-4 = [C6H2(CH2NMe2)2-2,6-R-4]− in which R = C2H2C6H4-R′-4′ with R′ = NPh2, NMe2, OMe, SiMe3 H, I, CN, NO2) (1−8), were studied for their electronic, electrochemical, and NLO properties. Complex 7 was also chemically oxidized using Cu(II)Cl2, yielding the [Pt(IV)Cl3(NCN(C2H2C6H4-CN-4′)-4)] complex 11. In contrast to 1 and 7, 11 did not show luminescent properties in solution at room temperature. In the solid state (X-ray crystallography) 11 has an overall bent structure, with the pincer moiety and the cyano group beneath the plane of the central double bond. Stilbenoid pincer complex 1 (R′ = NPh2) was also studied with UV/vis spectroscopy in a series of different solvents. The compound shows an intense low-energy transition band, appearing at a lower energy (λmax = 374–379 nm) than 2 (R′ = NMe2), which contains a stronger donor group. The UV/vis absorption data of a selected series of stilbenoid pincer platinum complexes were interpreted in terms of a qualitative orbital model based on DFT and TD-DFT calculations. The trends observed in the transition energies correlate well with the donor/acceptor properties of the substituents. It was shown that the HOMO–LUMO gap of the stilbenoid pincer platinum compounds decreases when going from an electron-neutral group (R′ = H) toward an electron-donating (R′ = NMe2) or -accepting (R′ = NO2) group. The fluorescence properties of 1 were also investigated using fluorescence and laser spectroscopy, showing that the metal center favors nonradiative decay from the excited state to the ground state. For 7 (R′ = CN), solid-state 13C CP/MAS NMR measurements were performed, and a value of 1 J(13C,195Pt) = 1003 ± 15 Hz was obtained for the C ipso carbon, reflecting π-contributions in the carbon−metal bond. The cyclic voltammetry study on the complexes revealed an irreversible oxidation from Pt(II) to Pt(IV). In general the oxidation potential is influenced by the electronic character of the R′ substituent. The influence of the para R′ substituent on the hyperpolarizability of the compound was investigated using the femtosecond (frequency-resolved) HRS technique. For 1−7 good β zzz values were measured (β zzz ranging from (164–1324) × 10−30 esu) with the highest value for 6 (R′ = I). The higher β zzz values were found for the compounds that contain a low-energy UV/vis absor |
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| ISSN: | 0276-7333 1520-6041 |
| DOI: | 10.1021/om700352z |