Remarkable Influence of the Cyclometalating Ligand on the Nuclearity and Properties of Heterobridged (渭-X)(渭-C鈮R) Platinum(II) Complexes

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• 作者：Jesu虂s R. Berenguer ; A虂lvaro Di虂ez ; Ana Garci虂a ; Elena Lalinde ; M. Teresa Moreno ; Sergio Sa虂nchez ; Javier Torroba
• 刊名：Organometallics
• 出版年：2011
• 出版时间：March 28, 2011
• 年：2011
• 卷：30
• 期：6
• 页码：1646-1657
• 全文大小：1160K
• 年卷期：v.30,no.6(March 28, 2011)
• ISSN：1520-6041

文摘

Partial dehalogenation reaction of [Pt(CN)(渭-Cl)]₂ [CN = 2,6-diphenylpyridinate (dppyH), 7,8-benzoquinolate (bzq)] with NaC鈮^tBu (or HC鈮^tBu/NEt₃/CuI) proceeds with formation of binuclear ([{Pt(dppyH)}₂(渭-Cl)(渭-C鈮^tBu)], 1) or tetranuclear ([Pt₂(bzq)₂(渭-Cl)(渭-C鈮^tBu)]₂, 4) complexes, depending on the nature of the cyclometalated ligand. Similar halide-bridged complexes 2, 3, 5, and 6 have also been prepared. The X-ray structures of 1, 4, and 5 reveal the selective formation in all cases of the isomer having the bridging chlorine atom located in a trans position to the metalated carbon atoms of two Pt(CN) units. In 4 and 5, the tetrahedral Pt₄ core is additionally stabilized by short Pt路路路Pt and 蟺路路路蟺 intramolecular bonding interactions, which have influence on their photophysical properties. The lower lying absorption bands are ascribed to mixed ¹MLCT [Pt鈫抎ppyH]/¹LL鈥睠T [C鈮R/X鈫抎ppyH] (complexes 1鈭?b>3) or to ¹MMLL鈥睠T transitions (L = C鈮R, L鈥?= bzq) (complexes 4鈭?b>6, TD-DFT). Complexes 1鈭?b>3 are nonemissive. By contrast, the tetranuclear clusters are brightly emissive at 77 K (solid state, frozen CH₂Cl₂), exhibiting an unstructured orange emission (560鈭?80 nm). This emission has been attributed, according to computational studies of the frontier orbitals in the optimized T₁ state of 5, to an excited state of large [Pt(d)/蟺(C鈮R)/Pt(d)鈫抌zq/bzq] character, with the LUMO delocalized on the adjacent Pt(bzq) fragments. In frozen CH₂Cl₂, an additional low-energy shoulder (640鈭?75 nm) is also detected, probably due to the presence of close distinct emissive states originating in small modifications in the ground-state structure in frozen solution.