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Upstream product

• 492-98-8 2,2'-biimidazole 
• 106-93-4 ethylene dibromide 
• 107-04-0 1-Bromo-2-chloroethane 

Relevant academic research and scientific papers

Molecular Scylla and Charybdis: Maneuvering between pH Sensitivity and Excited-State Localization in Ruthenium Bi(benz)imidazole Complexes

Bi(benz)imidazoles (b(b)im) acting as N,N-chelates in ruthenium complexes represent a unique class of ligands. They do not harbor metal-to-ligand charge-transfer (MLCT) excited states in ruthenium polypyridyl complexes upon visible-light excitation provided that no substitution is introduced at the N atoms. Hence, they can be used to steer light-driven electron-transfer pathways in a desired direction. Nonetheless, the free N atoms are susceptible to protonation and, hence, introduce highly pH-dependent properties into the complexes. Previous results for ruthenium complexes containing R2bbim ligands with alkylic or arylic N,N′-substitution indicated that, although pH insensitivity was accomplished, unexpected losses of spectator ligand features incurred simultaneously. Here, we report the synthesis and photophysical characterization of a series of differently N,N′-alkylated b(b)im ligands along with their corresponding [(tbbpy)2Ru(R2b(b)im)](PF6)2 complexes (tbbpy = 4,4′-tert-butyl-2,2′-bipyridine). The data reveal that elongation of a rigid ethylene bridge by just one methylene group drastically increases the emission quantum yield, emission lifetime, and photostability of the resultant complexes. Quantum-chemical calculations support these findings and allow us to rationalize the observed effects based on the energetic positions of the respective excited states. We suggest that N,N′-propylene-protected 1H,1′H-2,2′-biimidazole (prbim) is a suitable spectator ligand because it stabilizes sufficiently long-lived MLCT excited states exclusively localized at auxiliary bipyridine ligands. This ligand represents, therefore, a vital building block for next-generation photochemical molecular devices in artificial photosynthesis.

Synthesis of 2,2′-bIImidazole-based platinum(II) polymetallaynes and tuning their fluorescent response behaviors to Cu2+ ions through optimizing the configuration of the organic spacers and steric effect

Under controlled conditions, platinum(ii) polymetallaynes with different 2,2′-biimidazole-based organic spacers have been synthesized readily. Their photophysical properties and fluorescent response behaviors to Cu2+ ions have been investigated in detail. By adjusting both the configuration of the 2,2′-biimidazole-based spacers and the steric effect, the fluorescent response behaviors of the polymetallaynes to Cu2+ ions can be tuned dramatically. The fluorescent signal from the polymetallayne with an optimized structure can be quenched rapidly by Cu2+ ions with a high Stern-Volmer constant KSV of ca. 6.8 × 104 M-1 and a low detecting limit (DL) of ca. 0.99 ppm. These results not only highlight the great potential of these polymetallaynes as novel Cu2+ sensors, but also provide new strategies for optimizing the sensing abilities of the 2,2′-biimidazole-based ion sensors.

Synthesis and physico-chemical studies of complexes of Co(II), Ni(II), Cu(II) and Hg(II) with some azole based biheterocyclic ligands

The biheterocyclic ligands 1,1'-dimethylene-2, 2'-bisimidazole [BBIIM, L] and 2-(2'-pyridyl)indole [PyIn, L'] form complexes of the type [Co(L or L')2X2], [Ni(L or L')X2], [Cu(L or L')X2] and [Hg(L or L')X2], X=Cl, NCS. The complexes have been characterised on the basis of elemental analyses, conductivity measurement, magnetic susceptibility measurement [Gouy and VSM (vibrating sample magnetometer) method] and IR-FTIR, electronic, NMR (1H and 13C) and EPR spectral studies. The 1H and 13C NMR signals of the free ligands undergo downfield shifts on complexation. The IR-FTIR spectral data reveal the unidentate nature of NCS group, which coordinates to the metal through nitrogen. The high resolution CID mass spectrum of L and EIMS of L' reveal the molecular mass of the ligands and their fragmentation pattern also.

Bridged Derivatives of 2,2'-Biimidazole

The reaction of 2,2'-biimidazole with 1,n-dihaloalkanes or o-xylylene dibromide leads to a series of N,N'-bridged derivatives.When these substances are treated with a second equivalent of 1,n-dihaloalkane, a series of bis-annelated biimidazolium salts is obtained.The conformations of these species are discussed with regard to their electronic absorption spectra and their 300-MHz 1H NMR spectra.The barriers for conformational inversion are found to be lower than for the corresponding bis-annelated 2,2'-bipyridinium salts.The redox properties of these salts are measured in CH3CN and DMSO, and their reductions are found to become increasingly more difficult and less reversible as the system becomes less planar.These results are explained primarily based on the greater N,N'-distance in 2,2'-biimidazole as compared with 2,2'-bipyridine.