Synthesis, Structural, and Photophysical Studies of Phenylquinoline and Phenylquinolinyl Alkynyl Based Pt(II) Complexes

We present the synthesis, characterization, and photophysical properties
of two series of alkynyl–platinum­(II) complexes containing
the phenylquinoline (Hpq) or the cyclometalated phenylquinolinyl (pq)
ligand. Unusual monoanionic complexes (NBu4)­[Pt­(CCR)3­(Hpq)] (R = Tol 1, C6H4OMe-3 2, C6H4CF3-4 3) were generated in moderate yield by treatment of [Pt­(pq)­(μ-Cl)]2 with an excess of LiCCR (1:8), followed by subsequent
treatment with NBu4 in iPrOH. However, a similar reaction with LiCCtBu evolves with formation of [Pt­(pq)­(μ–κCα:​η2-CCtBu)]2 4. Related
dimers [Pt­(pq)­(μ–κCα:​η2-CCR)]2 (R = Tol 5, C6H4OMe-3 6, C6H4CF3-4 7) were
successfully prepared by modification of the reaction conditions.
Single-crystal studies were performed on 2, 4, and 5, revealing the presence of intramolecular (H···Pt and H···CC) and intermolecular Omethoxy···HHpq contacts in 2 and the formation of butterfly
structures in 4 and 5. In the tBu derivative 4, a shorter intramolecular
Pt···Pt separation was found [3.0936(3) Å in 4 vs 3.2109(3) Å in 5], which is related
to the nature of η2-alkynyl linkages (η2-asymmetrical in 4 vs η2-symmetrical in 5). Anionic 1–3 display bright emissions in rigid
media (solid, glass) with resolved side vibronic bands at 77 K. The
energy of the emissions (supported by computational studies on 2) allows us to ascribe these emissions primarily to a mixed
alkynyl–metal to the phenylquinoline 3[(L′
+ M)­LCT] excited state, being perturbed in 2 (solid)
by the intermolecular Omethoxy···HHpq contacts. Whereas diplatinum complexes 5–7 have no visible emission at 298 K in the solid state, 4 shows a structureless band (578 nm), which is significantly
red-shifted at 77 K (595 nm). Theoretical studies suggest a notable
distortion in the excited state in relation to S0 and identify
the emission within the dimetallacycle Pt2(CC)2 with alkynyl to pq charge-transfer 3[(MM + L′)­LCT]
[with minor 3IL (pq) contribution], whereas, in 5, the emission is tentatively ascribed to a mixture of 3L′LCT with minor 3MMLCT character. The emission
profiles observed in glassy solution for all 4–7 complexes (556–562 nm, CH2Cl2) and in the solid state for 6–7 are consistent with those exhibited by mononuclear related chromophores 3[(L′ + M)­LCT] (L′ = CCR, L = pq), suggesting
negligible contribution of the Pt···Pt interaction.

我们报道了两类含苯基喹啉（Hpq，phenylquinoline）或环金属化苯基喹啉基（pq，cyclometalated phenylquinolinyl）配体的炔基铂(II)配合物的合成、表征及光物理性质。通过将[Pt(pq)(μ-Cl)]₂与过量的炔基锂（LiC≡CR）按1:8的摩尔比反应，随后在异丙醇（iPrOH）中用四正丁基铵（NBu4）处理，以中等收率得到了罕见的单阴离子配合物(NBu4)[Pt(C≡CR)₃(Hpq)]（R = 甲苯基Tol 1、3-甲氧基苯基C₆H₄OMe-3 2、4-三氟甲基苯基C₆H₄CF₃-4 3）。然而，与炔基锂LiC≡CtBu的类似反应则生成了二聚体配合物[Pt(pq)(μ–κCα:η²-C≡CtBu)]₂ 4。通过优化反应条件，我们成功制备了另一组相关二聚体[Pt(pq)(μ–κCα:η²-C≡CR)]₂（R = Tol 5、C₆H₄OMe-3 6、C₆H₄CF₃-4 7）。对配合物2、4和5开展单晶衍射分析，结果显示配合物2中存在分子内（H···Pt与H···C≡C）及分子间甲氧基···H-pq（Omethoxy···HHpq）相互作用，而配合物4和5则形成了蝶形结构。在叔丁基衍生物4中，我们观测到更短的分子内Pt···Pt间距[4中为3.0936(3) Å，5中为3.2109(3) Å]，这与η²-炔基桥联的成键性质相关（4中为不对称η²配位，5中为对称η²配位）。单阴离子配合物1–3在刚性介质（固体、玻璃态）中于77 K下展现出明亮的发射，且具有分辨良好的振动侧带。结合对2的计算研究结果，我们将这类发射主要归因为混合的炔基-金属到苯基喹啉的3[(L′ + M)LCT]激发态，而配合物2（固体）的发射则因分子间甲氧基···H-pq相互作用而发生扰动。双核铂配合物5–7在298 K的固体状态下无可见发射，而配合物4则展现出无结构的发射带（578 nm），且在77 K下发生显著红移至595 nm。理论研究表明，相较于基态S0，该激发态存在显著的结构畸变，并将该发射归属于含Pt₂(C≡C)₂双金属环的、以炔基到pq的电荷转移3[(MM + L′)LCT]为主（伴随少量3IL（pq）组分）的激发态；而在配合物5中，其发射暂被归因为3L′LCT与少量3MMLCT特征的混合态。所有4–7号配合物在二氯甲烷（CH2Cl2）玻璃态溶液中的发射光谱（556–562 nm）以及6–7号配合物在固体状态下的发射轮廓，均与单核相关发色团3[(L′ + M)LCT]（L′ = C≡CR，L = pq）的发射特征一致，表明Pt···Pt相互作用的贡献可忽略不计。