Ruthenium-(II)/-(III) terpyridine complexes incorporating imine functionalities. Synthesis, structure, spectroscopic and electrochemical properties
Ruthenium-(II)/-(III) terpyridine complexes incorporating imine functionalities. Synthesis, structure, spectroscopic and electrochemical properties
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DOI：
10.1039/b000257g
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发表时间：
2000
期刊：
影响因子：
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通讯作者：
Biplab Mondal;Soma Chakraborty;P. Munshi;M. Walawalkar;G. K. Lahiri
中科院分区：
文献类型：
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作者：
Biplab Mondal;Soma Chakraborty;P. Munshi;M. Walawalkar;G. K. Lahiri
合成了一类新的钌三联吡啶配合物[RuII（trpy）（L1 - 6）Cl] 1 - 6（trpy = 2，2 ′ ∶ 6 ′，2 ′ ′-三联吡啶; L1 - 3 = o-− OC6H3（R）C（R ′）NCH2C6H5; L4 - 6 = o-− OC6H3（R）CH（R ′）NNC6H5;其中R = H或p-NO2，R ′ = H或CH3）.在配合物4 - 6中，含有NH间隔基o-− OC6H3（R）C（R ′）NNHC6H5的"游离"配体在与钌三联吡啶部分配位时发生了亚胺到偶氮的互变异构，而那些含有CH2间隔基的配体（HL 1 - 3）在配位时保持不变。抗磁性的中性配合物1 - 6在可见光区表现出强MLCT跃迁，在UV区表现出配体内跃迁。已观察到MLCT能带能量的显著偏移取决于配位L的配位场强度。该配合物在0.12 - 0.63 V的电位范围内显示可逆的钌（III）-钌（II）电对，在1.21 - 1.85 V（相对于SCE）的电位范围内显示准可逆的钌（IV）-钌（III）电对。与配位L1 - 3相比，配位L4 - 6的更高配位场强度反映在观察到的金属氧化还原过程中。在-1.3 V附近观察到配位三联吡啶的还原。在77 K的EtOH-MeOH（4 ∶ 1 v/v）溶液中，配合物在661 - 690 nm范围内的最低能量MLCT带显示出中等强度的发射。配合物的量子产率（Φ = 0.006 - 0.09）对配位L的性质相当敏感。氧化的配合物3+和6+已被分离在固态作为其高氯酸盐。3+的晶体结构表现出伪八面体反式几何构型，相对于L3的亚胺氮（N4）和trpy配体的中心吡啶基的相对配置。单电子顺磁配合物显示1 ∶ 1的电导率，并显示配体到金属的电荷转移带在600和400 nm附近和配体内跃迁在紫外区。分析了在77 K下观察到的对应于畸变八面体几何构型的菱形EPR谱，提供了轴向畸变参数（Δ）和菱形畸变参数（V）的值以及t2壳层内两个预期配位场跃迁（ν 1和ν 2）的能量。
A new class of ruthenium terpyridine complexes of the type [RuII(trpy)(L1–6)Cl] 1–6 (trpy = 2, 2′∶6′, 2′′-terpyridine; L1–3 = o-−OC6H3(R)C(R′)NCH2C6H5 and L4–6 = o-−OC6H3(R)CH(R′)NNC6H5; where R = H or p-NO2 and R′ = H or CH3) have been synthesized. The “free” ligands incorporating a NH spacer o-−OC6H3(R)C(R′)NNHC6H5 (HL4–6) have undergone imine to azo tautomerism on co-ordination to the ruthenium terpyridine moiety in the complexes 4–6, whereas those having a CH2 spacer (HL1–3) remain unaltered on co-ordination. The diamagnetic, neutral complexes 1–6 exhibit strong MLCT transitions in the visible region and intraligand transitions in the UV region. A significant shift in MLCT band energy has been observed depending on the ligand field strength of the co-ordinated L. The complexes display a reversible ruthenium(III)–ruthenium(II) couple in the potential range of 0.12–0.63 V and a quasi-reversible ruthenium(IV)–ruthenium(III) couple in the range of 1.21–1.85 V versus SCE. The higher ligand field strength of the co-ordinated L4–6 compared to the co-ordinated L1–3 is reflected in the observed metal redox processes. The reduction of the co-ordinated terpyridine has been observed near −1.3 V. The complexes exhibit moderately strong emissions from the lowest energy MLCT bands in the range 661–690 nm in EtOH–MeOH (4∶1 v/v) at 77 K. The quantum yields of the complexes (Φ = 0.006–0.09) are found to be reasonably sensitive to the nature of the co-ordinated L. The oxidised complexes 3+ and 6+ have been isolated in the solid state as their perchlorate salts. The crystal structure of 3+ exhibits pseudo-octahedral trans geometry with regard to the relative disposition of the imine nitrogen (N4) of L3 and the central pyridyl group of the trpy ligand. The one-electron paramagnetic complexes show 1∶1 conductivity and display ligand-to-metal charge transfer bands near 600 and 400 nm and intraligand transitions in the UV region. The observed rhombic EPR spectra at 77 K corresponding to the distorted octahedral geometry have been analysed to furnish values of axial (Δ) and rhombic (V) distortion parameters as well as the energies of the two expected ligand field transitions (ν1 and ν2) within the t2 shell.