Search results for "Derivative"
showing 10 items of 1074 documents
Linked amido-indenyl complexes of titanium
1996
Abstract Titanium complexes Ti( η 5 : η 1 -C 9 H 6 SiMe 2 NCMe 3 )X 2 (X = Cl, Me, CH 2 SiMe 3 , CH 2 Ph) containing the tert -amino-functionalized indenyl ligand C 9 H 6 SiMe 3 NCMe 3 have been synthesized by the reaction of the dilithium derivative Li 2 [C 9 H 6 SiMe 2 NCMe 3 ] with TiCl 3 (THF) 3 followed by oxidation or by the alkylation of the dichloro derivative. Unexpectedly, the reaction of C 9 H 6 (SiMe 3 )(SiMe 2 Cl) with TiCl 4 does not give Ti( η 5 -C 9 H 6 SiMe 2 Cl)Cl 3 .
Synthesis and characterization of mixed catecholate and 1,10-phenanthroline complexes of antimony(III), C6H4O2SbX·1,10-phenanthroline (X F, Cl, Br,…
1982
Abstract The title compounds have been easily synthesized by reacting antimony(III) catecholates, C 6 H 4 O 2 SbX, with 1,10-phenanthroline. The infrared spectra of the solids are in accordance with a chelating behaviour of the phenanthroline ligand and the molecular monomeric nature of the fluoride derivative. In the case of the chloride, and possibly also for X Br and I, infrared data are better interpreted admitting a consistent ionic SbX bond interaction. The conductance data for their methanolic solutions also indicate a distinctive behaviour of the fluoride derivative, this being weakly ionized, whereas the remaining halides behave as 1:1 electrolytes. The main features of the mass…
Macrocycles prepared from lithocholic acid, piperazine and isomeric pyridine dicarboxylic acids and their selective affinities towards sodium and pot…
2001
Abstract Two novel macrocycles prepared from lithocholic acid, piperazine and pyridine dicarboxylic acids (2,6- and 3,5-isomers), have been characterized by 13C NMR and ESI–MS techniques. In case of the pyridine-2,6-dicarboxylate derivative, the molecular formula of the cycle was C59H87O6N3 (I), while the pyridine-3,5-dicarboxylate derivative (II) was a trimeric structure by molecular mass when compared with I. Furthermore, cycle I showed a special affinity towards potassium cation, while II possessed significant proton and sodium cation recognition properties.
3α-Hydroxy-N-(3-hydroxypropyl)-5β-cholan-24-amide
2009
The title compound, C27H47NO3, is a (3-hydroxypropyl)amide derivative of naturally occurring enantiopure lithocholic acid (3-hydroxy-5-cholan-24-oic acid). The molecule contains four fused rings: three six-membered rings in chair conformations and one five-membered ring in a half-chair form. The two terminal six-membered rings are cis-fused, while other rings are trans-fused. The structure contains an intramolecular O—H O hydrogen bond and a similar hydrogen-bond framework to the corresponding deoxycholic and chenodeoxycholic acid derivatives. Intermolecular O— H O and N—H O interactions are also present in the crystal. This compound seems to have at least two polymorphic forms from a compa…
Ferrocene-quinoxaline Y-shaped chromophores as fascinating second-order NLO building blocks for long lasting highly active SHG polymeric films
2016
The first example of a Y-shaped ferrocene quinoxaline derivative with a surprisingly high and stable second harmonic generation (SHG) response in composite polymeric films is reported. The interesting quadratic hyperpolarizability values of different substituted Y-shaped chromophores are also investigated in solution by the EFISH technique.
Saturation of a spin-1/2 particle by generalized local control
2011
We show how to apply a generalization of Local control design to the problem of saturation of a spin 1/2 particle by magnetic fields in Nuclear Magnetic Resonance. The generalization of local or Lyapunov control arises from the fact that the derivative of the Lyapunov function does not depend explicitly on the control field. The second derivative is used to determine the local control field. We compare the efficiency of this approach with respect to the time-optimal solution which has been recently derived using geometric methods.
New amide and dioxopiperazine derivatives from leaves of Breynia nivosa
2017
The first chemical investigation of leaves of Breynia nivosa from Nigeria resulted in the isolation of two new amide derivatives breynivosamides A and B (1 and 2) and two new dioxopiperazine derivatives breynivosines A and B (4 and 5) together with seven known compounds (3, 6-11). The structures of the new compounds were elucidated by 1D, 2D NMR and HRESIMS data as well as by comparison with the literature. All isolated compounds were tested for the cytotoxic and antimicrobial activities. Only cristatin A (6) showed cytotoxicity against the L5178Y mouse lymphoma cell line with an IC50 value of 13.9μM while breynivosamide A (1) exhibited moderate antimicrobial activity against Mycobacterium …
Multifunctional Poly(ethylene glycol)s
2011
In the rapidly evolving multidisciplinary field of polymer therapeutics, tailored polymer structures represent the key constituent to explore and harvest the potential of bioactive macromolecular hybrid structures. In light of the recent developments for anticancer drug conjugates, multifunctional polymers are becoming ever more relevant as drug carriers. However, the potentially best suited polymer, poly(ethylene glycol) (PEG), is unfavorable owing to its limited functionality. Therefore, multifunctional linear copolymers (mf-PEGs) based on ethylene oxide (EO) and appropriate epoxide comonomers are attracting increased attention. Precisely engineered via living anionic polymerization and d…
Inhibition of c-MYC with involvement of ERK/JNK/MAPK and AKT pathways as a novel mechanism for shikonin and its derivatives in killing leukemia cells
2015
Leukemia remains life-threatening despite remarkable advances in chemotherapy. The poor prognosis and drug resistance are challenging treatment. Novel drugs are urgently needed. Shikonin, a natural naphthoquinone, has been previously shown by us to be particularly effective towards various leukemia cell lines compared to solid tumors. However, the underlying mechanisms are still poorly understood. Here, we investigated shikonin and 14 derivatives on U937 leukemia cells. Four derivatives (isobutyrylshikonin, 2-methylbutyrylshikonin, isovalerylshikonin and β,β-dimethylacrylshikonin) were more active than shikonin. AnnexinV-PI analysis revealed that shikonins induced apoptosis. Cell cycle G1/S…
Inverted energy gap law for the nonradiative decay in fluorescent floppy molecules: larger fluorescence quantum yields for smaller energy gaps
2019
A data survey on experimental fluorescence quantum yields of (multi)substituted dicyano-distyrylbenzenes in fluid solution evidences that non-radiative decay increases with the Franck-Condon energy (E-FC), being opposite to the conventional energy gap law. Quantum-chemistry indicates that this is controlled by access to the conical intersection (CI) following the Bell-Evans-Polanyi principle as a first-step approximation for this family of molecules; the variations in E-FC among the different compounds are found to be decisive, while those of E-CI are estimated to be weaker or even enhancing the effect. The current findings may have significant consequences for the design of molecules for o…