Search results for " SPECT"
showing 10 items of 11464 documents
Protonation of a Spherical Macrotricyclic Tetramine: Water Inclusion, Allosteric Effect, and Cooperativity
2017
The spherical macrotricyclic cryptand tetramine "C24" (1) displays remarkable protonation behaviour. It undergoes protonation in four successive steps for which pKa values of 11.17±0.05, 10.28±0.04, 6.00±0.06 and 3.08±0.08 have been determined at 298 K. The unusually close values for the first two protonations provide evidence for the encapsulation of a water molecule serving as effector for the second protonation, which is consistent with earlier observations that the exchange of protons bound in the diprotonated species with solvent protons is unusually slow and that 17 O NMR spectra show the presence of an oxygen centre in the same species quite distinct from that of solvent water. Encap…
Triorganotin( iv ) cation-promoted dimethyl carbonate synthesis from CO 2 and methanol: solution and solid-state characterization of an unexpected di…
2018
Two novel C,N-chelated organotin(IV) complexes bearing weakly coordinating carborane moieties were prepared by the reaction of the corresponding C,N-chelated organotin(IV) chloride (i.e. LCNR2SnCl, R = n-Bu (1) and Ph (2); LCN = 2-(N,N-dimethylaminomethyl)phenyl)) with monocarba-closo-dodecaborate silver salt (AgCB11H12; Ag·3). Both products of the metathesis, [LCN(n-Bu)2Sn]+[CB11H12]− (4) and [LCNPh2Sn]+ [CB11H12]− (5), respectively, were characterized by both multinuclear NMR spectroscopy and elemental analysis. The instability of 4 and 5 towards water is discussed. The solid-state structure of LCN(n-Bu)2SnOH·B(C6F5)3 (4a) as a model compound with a Sn–O(H)⋯B linkage is also reported. The…
Subphthalocyanine basicity: reversible protonation at the azomethine bridge
2017
International audience; Subphthalocyanine (SubPc) could be reversibly protonated at the azomethine bridge. This phenomenon was examined by addressing the pKa of the acid (TFA, MSA, TMSA) and the SubPc electron-withdrawing properties of the peripheral isoindolic substituents (F12 vs. H12 and NO2), which tunes the basic character of the azomethine moiety. The protonation of up to three azomethines was suggested and monitored spectrophotometrically with the appearance of new absorption bands at 610, 630 nm and 660 nm, together with marked colour changes from purple to blue to green. Evidence of such a protonation was also shown by significant changes in the 1H-NMR spectrum and new bands in the…
Synthesis, reactivity and structural studies of selenide bridged carboranyl compounds.
2006
Reaction of the lithium salt Li[1-R-1,2-closo-C(2)B(10)H(10)] with selenium under mild conditions, followed by hydrolysis gave the diselenide compound (1-Se-2-R-1,2-closo-C(2)B(10)H(10))(2) in contrast to the well-reported mercapto compounds 1-SH-2-R-1,2-closo-C(2)B(10)H(10) obtained using a similar synthetic procedure. Details for the preparation and X-ray structural characterisation of the new compounds (2-Me-1,2-closo-C(2)B(10)H(10))(2)Se, (1-Se-2-R-1,2-closo-C(2)B(10)H(10))(2) (R = Me, Ph, ) are specified. To further explore the mechanism of the dimerization reaction, the complex [Au(1-Se-2-Me-1,2-closo-C(2)B(10)H(10))(PPh(3))] was synthesized, confirming the existence of the intermedia…
Highly Stable Neutral and Positively Charged Dicarbollide Sandwich Complexes
2005
Novel sandwich metallacarboranes commo-[3,3'-Ni(8-SMe2-1,2-C2B9H10)2] (1), commo-[3,3'-Co(8-SMe2-1,2-C2B9H10)2]+ (2+), commo-[3,3'-Ru(8-SMe2-1,2-C2B9H10)2] (4) and commo-[3,3'-Fe(8-SMe2-1,2-C2B9H10)2] (5) have been prepared by reaction of [10-SMe2-7,8-nido-C2B9H10]- with NiCl2 x 6 H2O, CoCl2, [RuCl2(dmso)4] and [FeCl2(dppe)], respectively. Reduction of 2+ with metallic Zn leads to the neutral and isolable complex commo-[3,3'-Co(8-SMe2-1,2-C2B9H10)2] (3). Theoretical calculations using the ZINDO/1 semiempirical method show three energy minima for complexes 1-3 and 5 that agree with the presence of three different rotamers in solution at low temperature, while four relative energy minima have…
Effects of Remote Ligand Substituents on the Structures, Spectroscopic, and Magnetic Properties of Two-Coordinate Transition-Metal Thiolate Complexes
2018
The first-row transition-metal(II) dithiolates M(SAriPr4)2 [AriPr4 = C6H3-2,6-(C6H3-2,6-iPr2)2; M = Cr (1), Mn (3), Fe (4), Co (5), Ni (6), and Zn (7)] and Cr(SArMe6)2 [2; ArMe6 = C6H3-2,6-(C6H2-2,4,6-Me3)2] and the ligand-transfer reagent (NaSAriPr4)2 (8) are described. In contrast to their M(SAriPr6)2 (M = Cr, Mn, Fe, Co, Ni, and Zn; AriPr6 = C6H3-2,6-(C6H2-2,4,6-iPr3)2) congeners, which differ from 1 and 3-6 in having p-isopropyl groups on the flanking aryl rings of the terphenyl substituents, compounds 1 and 4-6 display highly bent coordination geometries with S-M-S angles of 109.802(2)° (1), 120.2828(3)° (4), 91.730(3)° (5), and 92.68(2)° (6) as well as relatively close metal-flanking …
N-Cobaltocenium Amide as Reactive Nucleophilic Reagent for Donor–Acceptor Bimetallocenes
2017
Deprotonation of the aminocobaltocenium ion [Cc-NH2]+ ([H-1]+) generates the nucleophilic imine CcNH (1). Reaction of 1 with acid chlorides R–COCl (R = Ph, Fc, and Cc+) yields the reference amide [Ph-CO-NH-Cc]+ (2+) and the amide-linked hetero- and homobimetallocenes [Fc-CO-NH-Cc]+ (3+) and [Cc-CO-NH-Cc]2+ (42+), respectively. Cation–anion interactions of charged amides 2+–42+ in the solid state and in solution are probed by single crystal X-ray diffraction and NMR and IR spectroscopy. Intramolecular metal–metal interactions in donor–acceptor heterobimetallocene 3+ and in mixed-valent homobimetallocene 4+ (prepared electrochemically) are discussed within the Marcus–Hush framework aided by s…
Size‐Selective Encapsulation of Hydrophobic Guests by Self‐Assembled M 4 L 6 Cobalt and Nickel Cages
2012
Subtle differences in metal-ligand bond lengths between a series of [M(4)L(6)](4-) tetrahedral cages, where M = Fe(II), Co(II), or Ni(II), were observed to result in substantial differences in affinity for hydrophobic guests in water. Changing the metal ion from iron(II) to cobalt(II) or nickel(II) increases the size of the interior cavity of the cage and allows encapsulation of larger guest molecules. NMR spectroscopy was used to study the recognition properties of the iron(II) and cobalt(II) cages towards small hydrophobic guests in water, and single-crystal X-ray diffraction was used to study the solid-state complexes of the iron(II) and nickel(II) cages.
Corrosion inhibition performance of a structurally well-defined 1,2,3-triazole derivative on mild steel-hydrochloric acid interface
2021
Abstract In the present work, a new 1,4-disubstituted-1,2,3-triazole product, named 4-[1-(4-methoxy-phenyl)-1H-[1,2,3]triazol-4-ylmethyl]-morpholine (MPTM) was successfully synthesized under click chemistry regime. The structure of the new compound that has a rigid triazole moiety and a flexible morpholine ligand has been characterized using 1H NMR, 13C NMR, HRMS, and FTIR spectroscopy. Its inhibition performance for mild steel in acidic medium 1 M HCl has been studied by utilizing a combination of experimental, spectroscopic and computational methods. The electrochemical characterization was carried out by a gravimetric study, electrochemical impedance spectroscopy (EIS), and potentiodynam…
Cis versus Trans: The Coordination Environment about the Tin(IV) Atom in Spirocyclic Amino Alcohol Derivatives.
2018
The syntheses of amino alcohols MeN(CH2 CH2 CMe2 OH)2 (1), MeN(CMe2 CH2 OH)(CH2 CMe2 OH) (2), MeN(CH2 CH2 CH2 OH)(CH2 CMe2 OH) (3), MeN(CH2 CH2 CMe2 OH)(CH2 CMe2 OH) (4), MeN(CH2 CH2 CMe2 OH)(CH2 CH2 OH) (5), and MeN(CH2 CH2 OH) (CH2 CH2 CH2 OH) (6) as well as spirocyclic tin(IV) alkoxides spiro-[nBuN(CH2 CMe2 O)2 ]2 Sn (7), spiro-[MeN(CH2 CH2 CMe2 O)2 ]2 Sn (8), spiro-[para-FC6 H4 N (CH2 CMe2 O)2 ]2 Sn (9), spiro-[MeN(CMe2 CH2 O)(CH2 CMe2 O)]2 Sn (10), spiro-[MeN(CH2 CH2 CH2 O)(CH2 CMe2 O)]2 Sn (11), spiro-[MeN(CH2 CH2 CMe2 O)(CH2 CMe2 O)]2 Sn (12), spiro-[MeN(CH2 CH2 CMe2 O)(CH2 CH2 O)]2 Sn (13) and spiro-[MeN(CH2 CH2 O)(CH2 CH2 CH2 O)]2 Sn (14) are reported. The compounds were characteri…