辅助配体对桥联双钌配合物电子结构和阴离子传感特性的影响。

Influence of ancillary ligands on the electronic structure and anion sensing features of ligand bridged diruthenium complexes.

机构信息

Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai-400076, India.

出版信息

Dalton Trans. 2013 Oct 7;42(37):13733-46. doi: 10.1039/c3dt50853f. Epub 2013 Aug 1.

Abstract

The present article deals with a newer class of ligand bridged asymmetric complexes incorporating ancillary ligands (AL) with varying electronic characteristics: (bpy)2Ru(II)(μ-HL(2-)) Ru(II)(bpy)22·(12); (pap)2Ru(II)(μ-HL(2-))Ru(II)(pap)22 (22); (bpy)2Ru(II)(μ-HL(2-))Ru(II)(pap)22 (32); [(acac)2Ru(III)(μ-HL(2-))Ru(III)(acac)2] (4) and [(bpy)2Ru(II)(μ-HL(2-))Ru(III)(acac)2]ClO4 ([5]ClO4) (H3L: 5-(1H-benzo[d]imidazol-2-yl)-1H-imidazole-4-carboxylic acid, bpy = moderately π-accepting 2,2'-bipyridine, pap = strongly π-accepting 2-phenylazopyridine, acac(-) = σ-donating acetylacetonate). The molecular identity of 12 was established by its single crystal X-ray structure. A large shift in Ru(II)/Ru(III) potential of 0.7-2.0 V took place on switching the ancillary ligands from AL = bpy to pap to acac(-), leading to the stabilisation of ruthenium(II) and ruthenium(III) states in 1(2+), 2(2+), 3(2+), 4 and 5(+), respectively. The detailed magnetic studies revealed that the paramagnetic Ru(III)Ru(III) state in 4 essentially behaves as a system with two independent S = 1/2 spins and it exhibits an anisotropic EPR at 77 K ( = 2.192, Δg = g1-g3 = 0.70) but without any half-field signal near g∼ 4. The isolated mixed valent Ru(II)Ru(III) state in 5(+) exhibits weak antiferromagnetic coupling of -0.25 cm(-1) and anisotropic EPR with = 2.155, Δg = 0.704 but fails to show a Ru(II)→ Ru(III) IVCT (intervalence charge transfer) transition in the near-IR region up to 2000 nm. The complexes 1(2+), 2(2+) and 4 encompassing identical metal fragments, exhibited weak to moderate electrochemical coupling at the intermediate mixed valent states with Kc values of 10(2)-10(5). The coulometrically generated mixed valent Ru(II)Ru(III) state in 1(3+) or 4(-) also failed to display any prominent absorption in the near-IR region, but exhibited Ru(III) based rhombic EPR, implying valence localised situation with negligible intermetallic electronic coupling. The complexes 2(2+), 3(2+), 4 and 5(+) having one NH proton associated with the bridging ligand HL(2-) do not show any interaction with the anions F(-), Cl(-), Br(-), I(-), HSO4(-), H2PO4(-), OAc(-) and SCN(-) in CH3CN, though 1(2+) selectively recognises the fluoride ion.

摘要

本文涉及一类新型的配体桥联不对称配合物，其中包含具有不同电子特性的辅助配体 (AL)：(bpy)2Ru(II)(μ-HL(2-))Ru(II)(bpy)22·(12); (pap)2Ru(II)(μ-HL(2-))Ru(II)(pap)22 (22); (bpy)2Ru(II)(μ-HL(2-))Ru(II)(pap)22 (32); [(acac)2Ru(III)(μ-HL(2-))Ru(III)(acac)2] (4) 和 [(bpy)2Ru(II)(μ-HL(2-))Ru(III)(acac)2]ClO4 ([5]ClO4) (H3L：5-(1H-苯并[d]咪唑-2-基)-1H-咪唑-4-羧酸，bpy = 中等π-接受 2,2'-联吡啶，pap = 强π-接受 2-苯并氮杂吡啶，acac(-) = σ-供体乙酰丙酮)。12 的分子身份通过其单晶 X 射线结构确定。当辅助配体从 AL = bpy 切换到 pap 到 acac(-) 时，Ru(II)/Ru(III) 电势能发生了 0.7-2.0 V 的大位移，导致 1(2+)、2(2+)、3(2+)、4 和 5(+)中分别稳定了钌(II)和钌(III)态。详细的磁性研究表明，4 中的顺磁 Ru(III)Ru(III)态本质上表现为两个独立 S = 1/2 自旋的系统，它在 77 K 时表现出各向异性 EPR ( = 2.192, Δg = g1-g3 = 0.70)，但在接近 g∼ 4 的地方没有任何半场信号。分离的混合价态 Ru(II)Ru(III)态在 5(+)中表现出较弱的反铁磁耦合-0.25 cm(-1) 和各向异性 EPR， = 2.155, Δg = 0.704，但在近红外区域 (2000 nm) 内没有显示出 Ru(II)→ Ru(III) IVCT (离域电荷转移) 跃迁。包含相同金属片段的 1(2+)、2(2+) 和 4 表现出在中间混合价态下的弱至中等电化学偶联，Kc 值为 10(2)-10(5)。1(3+) 或 4(-) 中电化学生成的混合价态 Ru(II)Ru(III)态也没有在近红外区域显示出任何明显的吸收，但表现出基于 Ru(III)的菱形 EPR，表明价态局部化，几乎没有金属间电子耦合。具有一个与桥联配体 HL(2-) 相关的 NH 质子的 2(2+)、3(2+)、4 和 5(+) 与阴离子 F(-)、Cl(-)、Br(-)、I(-)、HSO4(-)、H2PO4(-)、OAc(-) 和 SCN(-) 在 CH3CN 中没有相互作用，尽管 1(2+) 选择性地识别氟离子。