Search results for " Spectroscopy"
showing 10 items of 6851 documents
Conformational Switching of Multi-Responsive Ferrocenyl-Phenol Conjugates
2016
Multifunctional conformational switches based on the ferrocenyl-salicylic acid amide motif with increasing additional complexity at the Fc moiety (R = COOMe, CONHEt, CONHFc; H-2–H-4; Fc = ferrocenyl) have been prepared and their preferred secondary structures in solution have been elucidated by NMR and IR spectroscopy in combination with conformational searches based on DFT calculations. Their distinct conformational responses to deprotonation ([2]––[4]–) and oxidation ([H-2]+·–[H-4]+·) have been revealed by IR, EPR, and UV/Vis spectroscopy as well as by DFT calculations. Deprotonation inverts all amide units (double amide twist) whereas oxidation selectively flips the terminal amide unit (…
Diferratricarbaboranes of thesubcloso-[(η5-C5H5)2Fe2C3B8H11] Type, the First Representatives of the 13-Vertex Dimetallatricarbaborane Series
2003
Treatment of the [2-Cp-9-tBuNH-closo-2,1,7,9-FeC 3 B 8 H 1 0 ] (1) ferratricarbollide (Cp = η 5 -C 5 H 5 -) with Na + C 1 0 H 8 - in 1,2-dimethoxyethane (DME) at room temperature produced an air-sensitive transient anion with a tentatively identified nido-[tBUNH-CpFeC 3 B 8 H 1 0 ] 2 - constitution. In-situ reaction of this low-stability ion with [CpFe(CO) 2 I] or [CpFe(CO) 2 ] 2 generated three violet diferratricarbaboranes identified as paramagnetic subcloso complexes [4,5-Cp 2 - -4,5,1,6,7-Fe 2 C 3 B 8 H 1 1 ] (2; yield 2%), [4,5-Cp 2 - -4,5,1,7,12-Fe 2 C 3 B 8 H 1 1 ] (3; yield 2%), and [7-tBuNH-4,5-Cp 2 - -4,5,1,7,12-Fe 2 C 3 B 8 H 1 0 ] (4; yield 14%). These first representatives of t…
Protonation of Tyrosine Kinase Inhibitor Lapatinib: A Theoretical and Experimental Study
2019
The protonation process of tyrosine kinase inhibitor lapatinib was studied by means of 1HNMR and UV/Vis spectroscopy joint with the theoretical calculations at DFT and semi-empirical levels. DFT/M06-2X geometries were used to describe and compare the different cationic forms of lapatinib, while ZINDO/S-CI method performed on those geometries allowed for the interpretation of experimental UV/Vis spectra of lapatinib at various pH. We found that at low pH two different dicationic forms (N2N1 and N1N3) of lapatinib were present in ethanol and DMSO-d6 solutions. The first protonation, however, occurred on the aliphatic N1 in DMSO-d6, while in ethanol solutions most probably the quinazoline nitr…
Mixed phenoxo and azido bridged dinuclear nickel(II) and copper(II) compounds with N,N,O-donor schiff bases: Synthesis, structure, DNA binding, DFT a…
2019
Abstract Two dinuclear complexes, µ-phenoxo, µ1,1-azido bridged [Ni2(L)2(µ1,1-N3)(N3)(CH3OH)] (1) and µ-phenoxo, µ1,1-azido bridged [Cu2(L)2(µ1,1-N3)(N3)] (2) bearing HL as a blocking co-ligand produced by the 1:1 condensation of N-methyl 1,3 propanediamine with o-vanillin have been synthesized and successfully characterized by elemental analyses, IR and electronic spectroscopy, single-crystal X-ray diffraction for 1 and DFT optimization for 2. X-ray crystal structure discloses that the asymmetric unit of 1 consists of two nickel(II) ions exhibiting a six-coordinate octahedral coordination with µ-phenoxo, µ1,1-azido bridging dimeric structure. The DFT optimization of 2 reveals the five-coor…
Variable Cooperative Interactions in the Pressure and Thermally Induced Multistep Spin Transition in a Two-Dimensional Iron(II) Coordination Polymer
2020
Two types of experiments conducted to investigate the effect of pressure on the spin crossover (SCO) properties of the 2D Fe(II) coordination polymer formulated {Fe[bipy(ttr)2]}n are reported, namely, (1) magnetic measurements performed at variable temperature and at fixed pressure and (2) visible spectroscopy at variable pressure and fixed temperature. The magnetic experiments carried out under a hydrostatic pressure constraint of 0.04, 0.08, and 0.8 GPa reveal a two-step spin transition behavior. The characteristic critical temperatures of the spin transition are shifted upward in temperature as pressure increases. The slope of the straight-line of the Tc vs P plot, dTc/dP, is 775 K/GPa a…
Equipping metallo-supramolecular macrocycles with functional groups: Assemblies of pyridine-substituted urea ligands
2012
A series of di-(m-pyridyl)-urea ligands were prepared and characterized with respect to their conformations by NOESY experiments and crystallography. Methyl substitution in different positions of the pyridine rings provides control over the position of the pyridine N atoms relative to the urea carbonyl group. The ligands were used to self-assemble metallo-supramolecular M(2)L(2) and M(3)L(3) macrocycles which are generated in a finely balanced equilibrium in DMSO and DMF according to DOSY NMR experiments and ESI FTICR mass spectrometry. Again, crystallography was used to characterize the assemblies. Methyl substitution in positions next to the pyridine nitrogen prevents coordination, while …
A water molecule in the interior of a 1H-pyrazole Cu2+ metallocage
2016
Water has a great tendency to associate through hydrogen bonding with water molecules or other hydrogen bond donor or acceptor groups. Here the case of a water molecule encapsulated in the interior of a metallocage receptor is presented. The association of four copper(II) ions and two aza-macrocyclic receptors in which two 1H-pyrazole units are connected by cadaverine diamines leads to the inclusion of a water molecule into the cage, as proved by X-ray analysis and infrared spectroscopy. The included water molecule shows no hydrogen bonding with any component of the cage presenting only a weak hydrogen bond with an oxygen atom of a perchlorate counter-anion. The IR stretching vibrations pre…
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…