N,N'-Bis(3-triethoxysilyl)phthalic Diamide, N,N'-Bis(3-triethoxysilyl)malonic Damide and Derivatives

Condensation of 3-triethoxysilylpropylamine with malonic amide was studied. The condensation products, dicarboxylic acid diamides (malonic and phthalic), were used for peretherification with triethanolamine and thus new representatives of silatran series compounds were prepared: N,N'-bis(3-triethoxysilyl)malonic diamide and -phthalic diamide. By hydrolytic polycondensation of N,N'-bis(3-triethoxysilyl)malonic diamide we synthesized an organosilicon polymer with silsesquioxane structure, which we studied as a sorbent of platinum group metals rhodium, palladium and platinum. Peculiar features of sorption activity of the polymer and speculative mechanism of metal sorption are discussed.     

N,N''''-bis(3-Chlorophenyl)urea

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IR- und RAMAN-Spektren von CuN3, AgN3, TIN3, BiON3, Cu(N3)2 und α-Pb(N3)2

IR- and RAMAN Spectra of CuN₃, AgN₃, TlN₃, BiON₃, Cu(N₃)₂, and α-Pb(N₃)₂ The vibrational spectra of the title compounds were recorded and assigned with respect to their crystal structure. The RAMAN spectra mere obtained in aqueus sus-pension.     

Ultrafast excited-state dynamics of rhenium(I) photosensitizers [Re(Cl)(CO)3(N,N)] and [Re(imidazole)(CO)3(N,N)]+: diimine effects

Femto- to picosecond excited-state dynamics of the complexes [Re(L)(CO)(3)(N,N)](n) (N,N = bpy, phen, 4,7-dimethyl-phen (dmp); L = Cl, n = 0; L = imidazole, n = 1+) were investigated using fluorescence up-conversion, transient absorption in the 650-285 nm range (using broad-band UV probe pulses around 300 nm) and picosecond time-resolved IR (TRIR) spectroscopy in the region of CO stretching vibrations. Optically populated singlet charge-transfer (CT) state(s) undergo femtosecond intersystem crossing to at least two hot triplet states with a rate that is faster in Cl (～100 fs)(-1) than in imidazole (～150 fs)(-1) complexes but essentially independent of the N,N ligand. TRIR spectra indicate the presence of two long-lived triplet states that are populated simultaneously and equilibrate in a few picoseconds. The minor state accounts for less than 20% of the relaxed excited population. UV-vis transient spectra were assigned using open-shell time-dependent density functional theory calculations on the lowest triplet CT state. Visible excited-state absorption originates mostly from mixed L;N,N(?-) → Re(II) ligand-to-metal CT transitions. Excited bpy complexes show the characteristic sharp near-UV band (Cl, 373 nm; imH, 365 nm) due to two predominantly ππ*(bpy(?-)) transitions. For phen and dmp, the UV excited-state absorption occurs at ～305 nm, originating from a series of mixed ππ* and Re → CO;N,N(?-) MLCT transitions. UV-vis transient absorption features exhibit small intensity- and band-shape changes occurring with several lifetimes in the 1-5 ps range, while TRIR bands show small intensity changes (≤5 ps) and shifts (～1 and 6-10 ps) to higher wavenumbers. These spectral changes are attributable to convoluted electronic and vibrational relaxation steps and equilibration between the two lowest triplets. Still slower changes (≥15 ps), manifested mostly by the excited-state UV band, probably involve local-solvent restructuring. Implications of the observed excited-state behavior for the development and use of Re-based sensitizers and probes are discussed.