Probing d8-d8 Interactions in luminescent mono- and binuclear cyclometalated platinum(II) complexes of 6-phenyl-2,2′-bipyridines
Probing d8-d8 Interactions in luminescent mono- and binuclear cyclometalated platinum(II) complexes of 6-phenyl-2,2′-bipyridines
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DOI：
10.1021/ic990238s
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发表时间：
1999-09-06
影响因子：
4.6
通讯作者：
Che, CM
中科院分区：
文献类型：
--
作者：
Lai, SW;Chan, MCW;Che, CM
一系列发光单核和双核环合铂（II）配合物，即[Pt（L1-6）Cl]（1a-6a; HL 1 -6 = 4-（芳基）-6-苯基-2，2 '-联吡啶;芳基= H（1），苯基（2），4-氯苯基（3），4-甲苯基（4），4-甲氧基苯基（5），3，4，5-三甲氧基苯基（6）），[Pt（L-1）E]（+）（E = py（7），PPh3（8）），[Pt-2（L1-6）（2）（mu-dppm）]（2+）（1b-6 b，dppm =双（二苯基膦基）甲烷），[Pt-2（L-1）（2）（mu-pz）]（+）（9，Hpz =吡唑）和[Pt-2（L-1）（2）]（mu-dppcC（n））]（2+）（dppC（n）= bis（二苯基膦基）丙烷（10，n = 3）和-戊烷（11，n = 5）），以检查流体和固态低聚d（8）-d（8）和配体-配体相互作用。4 b（ClO_4）（2）和9（PF_6）的分子结构显示分子内Pt-Pt距离分别为3.245（1）和3.612（2）埃。虽然对于9预期最小的金属-金属通信，但弱的π-π相互作用是可能的。在这项工作中描述的所有配合物在室温下的流体溶液中是发射的。通过在6-苯基-2，2 '-联吡啶的4-位引入不同的芳基取代基，检测到发射能量的可忽略的变化，这表明它们之间几乎没有电子离域。在298 K二氯甲烷溶液中观察到单核衍生物对（MLCT）-M-3发射的自猝灭，在77 K乙腈溶液中观察到配合物7的发射能量的红闪.μ-dppm物质1b-6 b在λ（max）652-662 nm处的流体发射出现在比它们的单核对应物低得多的能量处，并且显示出显著的溶剂化变色效应。这些发射归因于（3）[d sigma*，pi*]激发态。相比之下，10和11的发射，轴承长桥接二膦配体，归因于非相互作用[Pt（L-1）]部分的（MLCT）-M-3状态。值得注意的是，μ-吡唑盐络合物9的发光显示出过渡特征，其使人联想到（3）[d σ *，pi*]和（MLCT）-M-3激发态。因此，在发射能量、最低能量激发态的性质和金属-金属相互作用之间观察到关系。通过电化学研究（1.61 V vs NHE）和芳烃淬灭实验（1.63 V vs NHE）估算了1b的激发态氧化还原电位[E（*Pt-2（2+）/Pt-2（+））]。
A series of luminescent mono- and binuclear cyclometalated platinum(II) complexes, namely [Pt(L1-6)Cl] (1a-6a; HL1-6 = 4-(aryl)-6-phenyl-2,2'-bipyridine; aryl = H (1), phenyl (2), 4-chlorophenyl (3), 4-tolyl (4), 4-methoxyphenyl (5), 3,4,5-trimethoxyphenyl (6)), [Pt(L-1)E](+) (E = py (7), PPh3 (8)), [Pt-2(L1-6)(2)(mu-dppm)](2+) (1b-6b, dppm = bis(diphenylpbosphino)methane), [Pt-2(L-1)(2)(mu-pz)](+) (9, Hpz = pyrazole), and [Pt-2(L-1)(2)(mu-dppcC(n))](2+) (dppC(n) = bis(diphenylphosphino)propane (10, n = 3) and -pentane (11, n = 5)), were synthesized in order to examine fluid- and solid-state oligomeric d(8)-d(8) and ligand-ligand interactions. The molecular structures of 4b(ClO4)(2) and 9(PF6) reveal intramolecular Pt-Pt distances of 3.245(1) and 3.612(2) Angstrom, respectively. While minimal metal-metal communication is expected for 9, weak pi-pi interactions are possible. All complexes described in this work are emissive in fluid solution at room temperature. Negligible changes in emission energy are detected by incorporating different aryl substituents into the 4-position of 6-phenyl-2,2'-bipyridine, and this indicates little electronic delocalization between them. Self-quenching of the (MLCT)-M-3 emission by the mononuclear derivatives are observed in CH2Cl2 at 298 K, and a red shia in the emission energy is exhibited by complex 7 in acetonitrile at 77 K. The fluid emissions of the mu-dppm species 1b-6b at lambda(max) 652-662 nm appear at substantially lower energies than their mononuclear counterparts and show dramatic solvatochromic effects. These emissions are ascribed to (3)[d sigma*, pi*] excited states. In contrast, the emission of 10 and 11, bearing long bridging diphosphine ligands, are attributed to (MLCT)-M-3 states of non-interacting [Pt(L-1)] moieties. Significantly, the luminescence of the mu-pyrazolate complex 9 displays transitional features which are reminiscent of both (3)[d sigma*, pi*] and (MLCT)-M-3 excited states. Hence a relationship is observed between emission energy, the nature of the lowest energy excited state, and metal-metal interactions. The excited-state redox potential [E(*Pt-2(2+)/Pt-2(+))] of 1b has been estimated by electrochemical studies (1.61 V vs NHE) and by quenching experiments with aromatic hydrocarbons (1.63 V vs NHE).