4591-56-4Relevant academic research and scientific papers
Self-assembly of bis-β-diketone-based [M2 L 2] dinuclear platforms into 2-dimensional coordination polymers
Brock,McMurtrie, John C.,Clegg
, p. 4786 - 4791 (2019)
A bis-β-diketone ligand incorporating a 3,5-substituted pyridine ring between its two β-diketone domains (1,1′-(pyridine-3,5-diyl)bis(4,4-dimethylpentane-1,3-dione), H2L1) and its interaction with three divalent cations (Cu2+, Zn2+ and Pd2+) is reported. Charge neutral dinuclear metallocycles of type [M2L12] were obtained in each case and their X-ray structures determined. [Pd2L12] incorporates two square-planar O4-coordinated metal centres. The zinc(ii) and copper(ii) complexes contain five-coordinate O4N1-metal centres in which the pyridyl nitrogen from adjacent [M2L12] metallocycles coordinates apically forming two-dimensional coordination polymers of type {[Zn2L12]n(dmf)n} and {[Cu2L12]n(dmf)n}. Desolvation of the coordination polymers led to loss of crystallinity.
Design, synthesis, and structural characterization of a new class of ferrocene-containing heterometallic triple-stranded helicates
Raja, Muthukrishna,Iyer, Ratnasabapathy G.,Gwengo, Chengeto,Reger, Daniel L.,Pellechia, Perry J.,Smith, Mark D.,Pascui, Andrea E.
, p. 95 - 103 (2013)
The new ditopic organoiron ligand, [3,5-bis(1-ferrocenyl-prop-3-enol-1-one) (pyridine)] (H2L3,5), has been prepared and the reactions of its dianion (Na2L3,5) with M3+ ions (M = Ga or In) yield a new class of "3d-np block" heterometallic triple-stranded helicates, M2(L3,5)3, by the self-assembly process. The X-ray structural analysis of the new ligand shows that it is in the enolic form with each enolic carbon bonded to the pyridine ring and each carbonyl carbon connected to a ferrocene moiety; overall, the nonferrocenyl part of the molecule is nearly planar. The M2(L 3,5)3 (M = Ga or In) complexes are helicates with three ligand strands, each of which is twisted into an S-shape, coordinating to two metal ions, each of which is in a distorted octahedral geometry. The new helicates are observed as a racemic mixture in the solid state by single-crystal X-ray analysis, and in solution by NMR, with both the left-handed Λ,Λ-and the right-handed Δ,Δ-isomers present. Variable-temperature 1H NMR study of the Ga2(L 3,5)3 helicate indicates that the right-handed Δ,Δ-isomer and left-handed Λ,Λ-isomer equilibrate through a heterochiral Λ,Δ-intermediate by a concerted twist motion of one-half of the dinuclear complex through a trigonal prismatic transition state, according to the Bailar twist mechanism. Electrochemical properties of the ligand (H2L3,5) and the M2(L 3,5)3 helicates were investigated through cyclic voltammetry, and the results indicate the lack of communication between the ferrocene units, because the separation between any two ferrocene units is greater than the 5-6 A range in both the free ligand and the helicates.
A porous supramolecular ionic solid
Chen, Ying-Pin,Chen, Yu-Sheng,Gao, Wen-Yang,Jackson, Nathan,Vazquez, Irma Rocio
supporting information, p. 7248 - 7251 (2021/07/28)
We report a synthetic strategy to integrate discrete coordination cages into extended porous materials by decorating opposite charges on the singular cage, which offers multidirectional electrostatic forces among cages and leads to a porous supramolecular ionic solid. The resulting material is non-centrosymmetric and affords a piezoelectric coefficient of 8.19 pC N?1, higher than that of the wurtzite ZnO.
Design and synthesis of cage-like NADH model molecule intermediate with multi-chiral centers
Zhang, Tong,Bai, Cui-Bing,Wu, Yue-Hua,Wang, Nai-Xing,Xu, Bao-Cai,Yan, Zhan,Xing, Yalan
supporting information, p. 410 - 416 (2019/02/05)
Studying NADH molecules is one of the most active areas in biomimetic research. It is important to design novel and efficient chiral NADH model molecules. Herein, a cage-like NADH model with multi-chiral centers was designed, and key intermediates have been synthesized. In this study, we found that pentafluorophenoxy group is an excellent leaving group for our synthetic route.
The flexibility-complementarity dichotomy in receptor-ligand interactions
Sun, Hongmei,Hunter, Christopher A.,Llamas, Eva Marina
, p. 1444 - 1453 (2015/02/19)
Synthetic supramolecular complexes provide an opportunity for quantitative systematic exploration of the relationship between chemical structure and molecular recognition phenomena. A family of closely related zinc porphyrin-pyridine complexes was used to examine the interplay of conformational flexibility and geometric complementarity in determining the selectivity of molecular recognition events. The association constants of 48 zinc porphyrin-pyridine complexes were measured in two different solvents, toluene and 1,1,2,2-tetrachloroethane (TCE). These association constants were used to construct 32 chemical double mutant cycles to dissect the free energy contributions of intramolecular H-bonds between the phenol side arms of the porphyrins and the ester or amide side arms of the pyridine ligands. Effective molarities (EM) for the intramolecular interactions were determined by comparison with the corresponding intermolecular H-bonding interactions. The values of EM do not depend on the solvent and are practically identical for amide and ester H-bond acceptors located at the same site on the ligand framework. However, there are variations of an order of magnitude in EM depending on the flexibility of the linker used to connect the H-bond acceptors to the pyridine ligands. Rigid aromatic linkers give values of EM that are an order of magnitude higher than the values of EM for the corresponding ester linkers, which have one additional torsional degree of freedom. However, the most flexible ether linkers give values of EM that are also higher than the values of EM for the corresponding ester linkers, which have one less torsional degree of freedom. Although the penalty for conformational restriction on binding is higher for the more flexible ether linkers, this flexibility allows optimization of the geometric complementarity of the ligand for the receptor, so there is a trade off between preorganization and fit.
Electron-deficient heteroarenium salts: An organocatalytic tool for activation of hydrogen peroxide in oxidations
?turala, Ji?í,Bohá?ová, Soňa,Chudoba, Josef,Metelková, Radka,Cibulka, Radek
, p. 2676 - 2699 (2015/03/18)
A series of monosubstituted pyrimidinium and pyrazinium triflates and 3,5-disubstituted pyridinium triflates were prepared and tested as simple catalysts of oxidations with hydrogen peroxide, using sulfoxidation as a model reaction. Their catalytic efficiency strongly depends on the type of substituent and is remarkable for derivatives with an electron-withdrawing group, showing reactivity comparable to that of flavinium salts which are the prominent organocatalysts for oxygenations. Because of their high stability and good accessibility, 4-(trifluoromethyl)pyrimidinium and 3,5-dinitropyridinium triflates are the catalysts of choice and were shown to catalyze oxidation of aliphatic and aromatic sulfides to sulfoxides, giving quantitative conversions, high preparative yields and excellent chemoselectivity. The high efficiency of electron-poor heteroarenium salts is rationalized by their ability to readily form adducts with nucleophiles, as documented by low pKR+ values (pKR+ red > -0.5 V). Hydrogen peroxide adducts formed in situ during catalytic oxidation act as substrate oxidizing agents. The Gibbs free energies of oxygen transfer from these heterocyclic hydroperoxides to thioanisole, obtained by calculations at the B3LYP/6-311++g(d,p) level, showed that they are much stronger oxidizing agents than alkyl hydroperoxides and in some cases are almost comparable to derivatives of flavin hydroperoxide acting as oxidizing agents in monooxygenases.
Oxidative activation of dihydropyridine amides to reactive acyl donors
Funder, Erik Daa,Trads, Julie B.,Gothelf, Kurt V.
, p. 185 - 198 (2015/01/16)
Amides of 1,4-dihydropyridine (DHP) are activated by oxidation for acyl transfer to amines, alcohols and thiols. In the reduced form the DHP amide is stable towards reaction with amines at room temperature. However, upon oxidation with DDQ the acyl donor is activated via a proposed pyridinium intermediate. The activated intermediate reacts with various nucleophiles to give amides, esters, and thio-esters in moderate to high yields. This journal is
Dissection of complex molecular recognition interfaces
Hunter, Christopher A.,Misuraca, Maria Cristina,Turega, Simon M.
supporting information; experimental part, p. 582 - 594 (2011/04/16)
The synthesis of a family of zinc porphyrins and pyridine ligands equipped with peripheral H-bonding functionality has provided access to a wide range of closely related supramolecular complexes featuring between zero and four intramolecular H-bonds. An automated UV/vis titration system was used to characterize 120 different complexes, and these data were used to construct a large of number of different chemical double mutant cycles to quantify the intramolecular H-bonding interactions. The results probe the quantitative structure-activity relationship that governs cooperativity in the assembly of complex molecular recognition interfaces. Specifically, variations in the chemical structures of the complexes have allowed us to change the supramolecular architecture, conformational flexibility, geometric complementarity, the number and nature of the H-bond interactions, and the overall stability of the complex. The free energy contributions from individual H-bonds are additive, and there is remarkably little variation with architecture in the effective molarity for the formation of intramolecular interactions. Intramolecular H-bonds are not observed in complexes where they are geometrically impossible, but there are no cases where excellent geometric complementarity leads to very high affinities. Similarly, changes in conformational flexibility seem to have limited impact on the values of effective molarity (EM). The major variation that was found for all of the 48 intramolecular interactions that were examined using double mutant cycles is that the values of EM for intramolecular carboxylate ester-phenol H-bonds (200 mM) are an order of magnitude larger than those found for phosphonate diester-phenol H-bonds (30 mM). The corresponding intermolecular phosphonate diester-phenol H-bonds are 2 orders of magnitude more stable than carboxylate ester-phenol H-bonds, and the large differences in EM may be due to some kind of compensation effect, where the stronger H-bond is harder to make, because it imposes tighter constraints on the geometry of the complex.
Use of the curtius rearrangement of acryloyl azides in the synthesis of 3,5-disubstituted pyridines: Mechanistic studies
Chuang, Ta-Hsien,Chen, Yu-Chi,Pola, Someshwar
experimental part, p. 6625 - 6630 (2010/11/18)
A series of disubstituted pyridine derivatives was synthesized from the corresponding acryloyl azides by acetic acid-promoted cycloaddition. This represents a novel and convenient synthetic approach to the symmetric 3,5-disubstituted pyridines. The nature of the substituent on the double bond and the utilized solvent were found to be crucial to the yield of pyridines. The reactivity of the acid-promoted cycloaddition increases with the presence of aryl groups, such as phenyl and pyridinyl. We also explored the comprehensive mechanism by the acid-promoted cycloaddition of 13C-labeled cinnamoyl azide. The symmetric 3,5-disubstituted pyridines were synthesized from acryloyl azides by acetic acid-promoted trimolecular condensation.
A novel NADH model: Design, synthesis, and its chiral reduction and fluorescent emission
Wang, Nai-Xing,Zhao, Jia
scheme or table, p. 3045 - 3050 (2010/04/28)
A novel chiral nicotinamide adenine dinucleotide hydrogen (NADH) model with C3 symmetry was designed and synthesized. Hydrogens at the C-4 position of all dihydropyridine rings in the inner part of the bowl could transfer to the substrate with powerful enantioselectivity. This novel C 3 symmetrical NADH model is capable of fluorescence emission at 455 nm when excited at 390 nm.
