Karmakar Srikanta, Maity Dinesh, Mardanya Sourav, Baitalik Sujoy
Department of Chemistry, Inorganic Chemistry Section, Jadavpur University , Kolkata 700032, India.
Inorg Chem. 2014 Nov 17;53(22):12036-49. doi: 10.1021/ic501741r. Epub 2014 Nov 6.
A symmetrical bridging ligand, 5,11-bis(4-([2,2':6',2″-terpyridine]-4'-yl)phenyl)-4,12-dihydropyreno[4,5-d:9,10-d']diimidazole (tpy-H2PhImzPy-tpy), containing terpyridyl coordinating units connected via a pyrenyl-bis-phenylimidazole spacer have been designed to synthesize a new class of light harvesting bimetallic Ru(II) complexes. The electronic properties of this complexes can be fine-tuned by varying tridentate terminal ligands. Full characterization of the compounds has been done with the help of (1)H NMR spectroscopy, high-resolution mass spectrometry, and elemental analysis. Geometry optimization of the complexes was also carried out with density functional theory (DFT). Electronic absorption spectra exhibit a number of very intense π-π* and n-π* transitions in the UV and moderately intense MLCT and ILCT transitions in the visible region. Interestingly, the present bimetallic complexes exhibit moderately strong luminescence in the range between 657 and 703 nm and lifetimes (long component) between 5.8 and 67.0 ns at room temperature showing the dependence of the emission characteristics upon the type of terminal ligand and solvent. Detailed temperature-dependent emission measurements showed that an overall enhancement of photoluminescence intensity and lifetime occur in all three cases upon lowering of temperature. The redox behavior of the compounds is characterized by a single reversible anodic wave corresponding to two closely spaced one-electron processes. The appearance of intervalence charge transfer transition (IVCT) bands in the NIR region on electrochemical generation of Ru(II)Ru(II)/Ru(II)Ru(III) species indicates the presence of substantial electronic communication among the two ruthenium centers in the bimetallic complexes. DFT and TDDFT calculations were also done for better understanding of the absorption and emission spectral characteristics of the complexes.
一种对称桥连配体，5,11-双(4-([2,2':6',2″-三联吡啶]-4'-基)苯基)-4,12-二氢芘并[4,5-d:9,10-d']二咪唑(tpy-H2PhImzPy-tpy)，其包含通过芘基-双-苯基咪唑间隔基连接的三联吡啶配位单元，已被设计用于合成一类新型的光捕获双金属Ru(II)配合物。通过改变三齿端基配体可以对该配合物的电子性质进行微调。借助(1)H NMR光谱、高分辨率质谱和元素分析对化合物进行了全面表征。还利用密度泛函理论(DFT)对配合物进行了几何优化。电子吸收光谱在紫外区域呈现出许多非常强烈的π-π和n-π跃迁，在可见光区域呈现出中等强度的MLCT和ILCT跃迁。有趣的是，目前的双金属配合物在室温下在657至703 nm范围内呈现出中等强度的发光，寿命（长组分）在5.8至67.0 ns之间，表明发射特性取决于端基配体的类型和溶剂。详细的温度依赖性发射测量表明，在所有三种情况下，随着温度降低，光致发光强度和寿命都会整体增强。化合物的氧化还原行为由对应于两个紧密间隔的单电子过程的单个可逆阳极波表征。在Ru(II)Ru(II)/Ru(II)Ru(III)物种的电化学生成过程中，近红外区域出现价间电荷转移跃迁(IVCT)带，表明双金属配合物中两个钌中心之间存在大量电子通讯。还进行了DFT和TDDFT计算，以更好地理解配合物的吸收和发射光谱特征。
