Time-resolved photoacoustics study of the ruthenium(II) bis(2,2'-bipyridine)(4,4'-dicarboxy-2,2'-bipyridine) complex

The formation and the decay of the triplet metal to ligand charge transfer state ((3)MLCT) of ruthenium(II) bis(2,2'-bipyridine)(4,4'-dicarboxy-2,2'-bipyridine) (Ru(bpy)(2)(dcbpy)) were characterized using photoacoustic calorimetry. At pH 6 and 2, the (3)MLCT state formation leads to a volume change of -8 mL mol(-1) and enthalpy changes of 17 kcal mol(-1) and 13 kcal mol(-1), respectively. We attribute the volume contraction to structural changes and to solvent electrostriction. At pH 4, the photoexcitation of the complex leads to an expansion of 14 mL mol(-1) and an enthalpy change of approximately 119 kcal mol(-1) due to protonation of the carboxyl group in the excited state.     

Bis(2,2′-bipyridine)(4,4′-diuntriacontanyl-2,2′-bipyridine)-ruthenium(II) chloride and related hydrophobic complexes

Summary New synthetic routes to 1-triacontanol and 1-bromotriacontane, and the novel ligands 4,4-diuntriacontanyl-2,2-bipy-ridine, 4-untriacontanyl-4'-methyl-2,2'-bipyridine and 4,4-ditricosyl-2,2-bipyridine are reported, as well as the preparation of the novel ruthenium(II) salts, [Ru(bipy)₂(bipy-4-R-4-R)]Cl₂ (bipy = 2,2'-bipyridine; R = R' = C₃₁H₆₃ or C₂₃H₄₇; R = C₃₁H₆₃, R' = Me).     

Geometric isomerism of copper(II) with monochlorobenzhydrazide chelate complexes

Summary Chelate complexes having a 12 Cu^II ion:(singly deprotonated ligand ratio, formed from Cu^II including 2-, 3- and 4-chlorobenzhydrazides, (ClC₆H₄C(O)NHNH₂) have been studied in the pH > 10 region. With the 2-chloro substituted derivative the cis-isomer is formed, whereas with the 3- and 4-chloro substituted derivatives trans-isomers are formed. The complexing schemes are described.     

Oxidative C-H and C-C bond cleavage by a (2,2'-bipyridine)copper(I) chloride complex

Acetonitrile is easily oxygenated at ambient reaction conditions to copper(II) oxalate [Cu(bpy)(ox)] n mediated by copper(I) chloride in the presence of 3,5-di-tert-butylcatechol and 2,2'-bipyridine. In the case of other nitriles (e.g., propionitrile), instead, the unusual and selective 1,4-extradiol cleavage of 3,5-di-tert-butylcatechol occurs to give copper(II) tert-butylmaleate [Cu(bma)(bpy)(H2O)]n in good yield.     

Mechanochromic luminescence switch of platinum(II) complexes with 5-trimethylsilylethynyl-2,2'-bipyridine

Planar platinum(II) complexes Pt(bpyC≡CSiMe(3))(C≡CC(6)H(4)R-4)(2) (R = H (1), Bu(t) (2)) with 5-trimethylsilylethynyl-22'-bipyridine show an unusual, reversible, and reproducible mechanical stimuli-responsive color and luminescence switch. When crystalline 1 or 2 is ground, bright yellow-green emitting is immediately converted to red luminescence with an emission red shift of 121-155 nm for 1 or 53-89 nm for 2. Meanwhile, the crystalline state is transformed to an amorphous phase that can be reverted to the original crystalline state by organic vapor adsorbing or heating, along with red luminescence turning back to yellow-green emitting. The reversibility and reproducibility of luminescence mechanochromic properties have been dynamically monitored by the variations in emission spectra and X-ray diffraction patterns. The drastic grinding-triggered emission red shift is likely involved in the formation of a dimer or an aggregate through Pt-Pt interaction, resulting in a conversion of the (3)MLCT/(3)LLCT emissive state in the crystalline state into the (3)MMLCT triplet state in the amorphous phase. Compared with the drastic grinding-triggered emission red shift in 1 (121-155 nm), the corresponding response shift in 2 (53-89 nm) is much smaller since a bulky tert-butyl in C≡CC(6)H(4)bu(t)-4 induces the planar platinum(II) molecules to stack through a longer Pt-Pt distance and less intermetallic contact compared with that in 1, as suggested from EXAFS studies.