A New Family of Ruthenium(II) Polypyridine Complexes Bearing 5-Aryltetrazolate Ligands as Systems for Electrochemiluminescent Devices

Abstract

A new family of mono- and dinuclear ruthenium polypyridyl complexes containing 5-aryltetrazolate ligands such as the deprotonated form of 4-(1H-tetrazol-5-yl)benzonitrile (4-TBNH) and bis(1H-tetrazol-5-yl)benzene (BTBH(2)) have been synthesized and thoroughly characterized. The reactivity of the mononuclear species toward different electrophiles such as H(+) and CH(3)(+) has been investigated, and the effects of the resulting regioselective electrophilic attacks on the electronic and structural properties of the tetrazolate ligand have been studied by NMR ((1)H, (13)C) spectroscopy and X-ray crystal structures. Absorption and emission spectroscopy, together with an electrochemical and UV-vis-NIR spectroelectrochemical investigation of the uncoordinated ligand and complexes, has been performed, highlighting a rather good luminescence efficiency and a poor bridge-mediated electronic communication between the metal centers of the dinuclear complexes. The electrogenerated chemiluminescence (ECL) of the dinuclear species has been explored, and for one of these, an exceptionally high ECL efficiency has been observed, comparable to that of [Ru(bpy)(3)](2+), which is considered a standard in ECL studies.

Electrochemiluminescent Systems as Devices and Sensors

“…Similar observations have been reported for binuclear Ru(II) complexes with weak interaction between both metallic centers. [84][85][86][87][88] These results indicate that further studies in such direction may result in design of still more efficient ECL systems based on Ru(II) luminophores.…”

Versatility of Terpyridine‐Functionalised Aryl Tetrazoles: Photophysical Properties, Ratiometric Sensing of Zinc Cations and Sensitisation of Lanthanide Luminescence

“…For this reason, tetrazoles are considered to be more metabolically stable bioisosteres of carboxylic acids . The presence of four sp 2 ‐hybridised lone pairs on the nitrogen atoms allows the construction of complex molecular architectures by bridging multiple metal ions, and many of these examples have been reported for species containing both transition metals and lanthanide elements …”

Ruthenium(II) Complexes Containing Tetrazolate Group: Electrochemiluminescence in Solution and Solid State

“…Ru(4-TBN)Ru shows two reversible oxidation processes and two very close reduction waves assigned to weakly interacting Ru centers bridged by the asymmetric ligand. 2 Fluorescence, ECL, and electrochemical data for all complexes and the reference one are summarized in Table 1. All molecules evidenced a smaller energy gap [E I,ox -E I,red ], expressed in eV with respect to the reference, and the ECL maximum wavelength is always red shifted with respect to Ru(bpy) 3 2+ .…”

“…1, 2 The intense emission of light generated by annihilation in organic solvents or in the presence of coreactant in water 3 has been extensively studied. The potential applications are correlated with the specific properties of the single compound.…”