The Imidazole Role in Strontium β-Diketonate Complexes Formation

Abstract

A selection of new strontium beta-diketonate derivatives (imH2)2[Sr2(beta-dike)6] [where imH = imidazole and beta-dike = tfac (tfacH = 1,1,1-trifluoro-2,4-pentanedione), tfbz (tfbzH = 1,1,1-trifluoro-4-phenyl-2,4-butanedione), or hfac (hfacH = 1,1,1,5,5,5-hexafluoro-2,4-pentanedione)], [Sr2(tfac)4(Meim)2(H2O)2], (MeimH)2[Sr(beta-dike)4] (where Meim = 1-methylimidazole and beta-dike = tfbz or hfac), [Sr2(thd)4(imH)2(EtOH)], and [Sr2(thd)4(Meim)2(EtOH)] (where thdH = 2,2,6,6-tetramethyl-3,5-heptanedione) have been synthesized and fully characterized. (imH2)2[Sr2(beta-dike)6] and (MeimH)2[Sr(beta-dike)4] are di- and mononuclear Sr anionic complexes, respectively, while [Sr2(tfac)4(Meim)2(H2O)2], [Sr2(thd)4(imH)2(EtOH)], and [Sr2(thd)4(Meim)2(EtOH)] are neutral dinuclear molecular derivatives. The derivative (imH2)2[Sr2(hfac)6] slowly decomposes in solution under aerobic conditions, giving (imH2)2[Sr(H2O)2(tfa)3](tfa) (tfaH = trifluoroacetic acid), which is an ionic compound containing polynuclear anionic chains composed of Sr(H2O)2(tfa)3 units. When a deficiency of imH is employed, the thdH proligand forms not only the dinuclear derivative [Sr2(thd)4(imH)2(EtOH)] but also an additional product with the formula [Sr(thd)2(H2O)2(EtOH)], in which the Sr atom is seven-coordinated. A complete solid-state characterization has been accomplished by comparing X-ray and solid-state 13C NMR data. Elucidation of the H-bond interaction between the heterocyclic rings and metal complexes by cross-polarization magic-angle-spinning 15N NMR is also reported.

Porous Titania Ionic Nanoparticle Networks

“…The reaction can indeed be followed in 15 N NMR by a characteristic downfield shift of the peak of the nitrogen directly linked to the methyl group. This downfield shift of 9 ppm between imidazole and imidazolium nitrogen was also reported in the literature. − …”

“…This downfield shift of 9 ppm between imidazole and imidazolium nitrogen was also reported in the literature. [31][32][33][34][35] As mentioned above, the CP MAS 15 N NMR spectrum of TiO 2 _Im þ Clrevealed the presence of remaining nonreacted imidazole units. For the unreacted imidazole groups, in this solidstate 15 N spectrum, only the peak corresponding to the nitrogen directly linked to the methyl can be observed, at 144 ppm.…”

“…This phenomenon was also reported in literature. 32,33 Due to the very low natural abundance of the 15 N isotope, namely 0.368%, as well as the low amount of nitrogen atoms in the material, the solid-state MAS 15 N NMR spectrum was recorded under cross-polarization (CP) conditions. The crosspolarization aims to increase the signal-to-noise ratio and to shorten the measurement time by transferring the magnetization of neighboring hydrogen atoms to the probed nucleus, nitrogen.…”

A novel two-dimensional layered framework built of strontium(II) with 4-nitrobenzene-1,3-dicarboxylic acid

“…The dihedral angle between the two basal planes (O2D/O3/O4 and O1A/O4C/O7) is 18.38 (15) , and the vertical distances between the two capping atoms, O2E and O3B, and their side planes O1A/O2D/O3/O4C and O1A/O2D/O4/O7 are 2.061 (3) and 1.847 (3) A Ê , respectively. The SrÐO bond distances fall in the range 2.458 (3)±2.783 (3) A Ê (mean 2.600 A Ê ; Table 1) and are all within the range of those observed for other eightcoordinated Sr II complexes with O-donor ligands (Davies et al, 2001;Deng et al, 2005;Marchetti et al, 2006;Stahl et al, 2006).…”

Synthesis and characterization of lead(II) complexes with substituted 2,2′-bipyridines, trifluoroacetate, and furoyltrifluoroacetonate

“…Compound 1 is a decomposition product, arising from cleavage of ''ftfa -'' and formation of ''tfac -''. Examples of the cleavage of fluorinated -diketonates to form the trifluoroacetate, by action of water during complex formation, are well-known [17]. Compound 1 is a polynuclear chain where Pb's are interconnected through bridging ''tfac -''.…”