ABSTRACT
Synthesis of quinoline-containing spiropyrrolizine was achieved via a 1,3-dipolar cycloaddition reaction of azomethine ylide (generated in situ from ninhydrin and l-proline) and (E)-2-styrylquinoline. The synthesized compounds were characterized by 1H NMR, 13C NMR, HRMS, and single-crystal XRD analysis. The XRD data revealed that the solid-state structures of the compounds belong to the monoclinic system of the space group P21/c and are stabilized through various weak noncovalent interactions such as C-H···O, C-H···π, and π···π interactions. The noncovalent interactions are characterized and quantified through Hirshfeld surface analysis. Moreover, the interaction energies of the intermolecular noncovalent interactions are calculated through PIXEL calculation. The PIXEL calculation provides precise interaction energy with an energy decomposition scheme. Energy Framework calculations have also been performed to delve deeper into understanding the intermolecular interactions. The intermolecular interactions are further characterized using Bader's theory of "atoms in molecules" (QTAIM) and the "noncovalent" (NCI) interaction plot index. The nature and strength of noncovalent interactions are analyzed from the topological parameters at (3, -1) bond critical points (BCPs).
ABSTRACT
Two fluorescence active bromoaniline-based Schiff base chemosensors, namely, (E)-4-bromo-2-(((4-bromophenyl)imino)methyl)phenol (HL1 ) and (E)-2-(((4-bromophenyl)imino)methyl)phenol (HL2 ), have been employed for the selective and notable detection of Cu2+ and Zn2+ ions, respectively, with the simultaneous formation of two new metal complexes [Cu(L1)2] (1) and [Zn(L2)2] (2). X-ray single crystal analyses indicate that complexes 1 and 2 are tetra-coordinated systems with substantial CH...π/π...π stacking interactions in the solid-state crystal structures. These two complexes are exploited for the next step detection of Al3+ and Hg2+ where complex 2 exhibits impressive results via turn-off fluorescence quenching in (DMSO/H2O) HEPES buffer medium. The sensing phenomena are optimized by UV-vis spectral analyses as well as theoretical calculations (density functional theory and time-dependent density functional theory). The combined detection phenomena of the ligand (HL2 ) and complex 2 are exclusively utilized for the first time to construct a molecular memory device, intensifying their multisensoric properties. Furthermore, the DNA- and human serum albumin (HSA)-binding efficacies of these two complexes are examined by adopting electronic and fluorometric titration methods. Complex 2 shows a higher DNA-binding ability in comparison with complex 1, whereas in the case of HSA, the reverse situation is observed. Finally, the binding modes of both the complexes with DNA and HSA have been investigated through molecular docking studies, suggesting good agreement with the experimental results.
ABSTRACT
Two Cu(II)-malonate complexes with 2-amino-4-methylpyridine (complex 1) and 2-aminopyrimidine (complex 2) auxiliary ligands were synthesized, and their single-crystal X-ray diffraction structures were established. Change in the auxiliary ligand exhibits substantial structural variation in the present complexes. Complex 1 shows a one-dimensional anionic copper-malonate moiety connected by the malonate bridge, whereas complex 2 is a mononuclear one. For both the complexes, auxiliary ligands are attached with the Cu-malonate moiety through various noncovalent interactions. Optical band gap, electrical conductivity, and photosensitivity of complexes 1 and 2 were measured, but the values of electrical parameters of the complexes significantly differ from each other. However, the magnitudes of electrical parameters increase several times for both the complexes when they are exposed under visible light, though the values of light sensing parameters of complex 1 were found to be higher than those of complex 2. Density functional theory calculations for complex 1 were carried out to support the experimental result.
ABSTRACT
Described in this work is the synthesis of a novel dicyano-substituted N-2-aminoethyl-4-(3-pyridinyl)-2-pyridone organic compound (1) that is characterized by several spectroscopic methods. Compound (1) was utilized for the preparation of its perchlorate (2), chloride (3), and bromide (4) salts. Single-crystal X-ray structures of these three salts were determined, and noncovalent weak interactions involving the aromatic rings, anions, and water molecules in (2-4) were investigated in detail. Solid-state UV-vis spectrum of the reported compounds (1-4) was utilized to calculate their optical band gaps, which clearly indicated that they belong to the semiconductor family. Under illumination condition, the magnitudes of electrical properties of (1) and its salts (2-4) improve remarkably although the improvement differs from salt to salt and the result was analyzed theoretically. Salt (2) was tested for its DNA binding ability.
ABSTRACT
Three salts [perchlorate (2), chloride (3) and tetrafluoroborate (4)] were synthesized from a 1-(2-aminoethyl)-6-hydroxy-2-oxo-1,2-dihydro-[4,4'-bipyridine]-3,5-dicarbonitrile compound (1) and characterized by spectroscopic and single crystal X-ray diffraction methods. Various noncovalent interactions (e.g., anionâ¯π+, πâ¯π, lpâ¯π) are explored in the solid state crystal structure of the salts. Optical band gaps of all the four compounds were determined from their solid-state UV-vis spectrum. Electrical properties like electrical conductivity, photosensitivity, etc. were calculated and the results revealed that they have potential to act as optoelectronic devices. The values of the electrical parameters increase several times when they are exposed to visible light rather than in dark conditions. The light sensing properties of the salts (2-4) are enhanced compared to that of the mother organic compound 1 but the magnitude of this enhancement is not same for the three salts. This observation has been rationalized by theoretical considerations. Moreover, the DNA binding ability of one of the representative salts (compound 2) was examined to check the biological importance of the synthesized salts.
ABSTRACT
Single crystal X-ray diffraction studies reveal the formation of six new coordination polymers (CPs) with the general formulas [Dy(3,5-pdc)(3,5-pdcH)(H2O)2]n·nH2O (1), [Pr2(3,5-pdc)3(H2O)2]n·2n(H2O) (2), [Sm2(3,5-pdc)3(H2O)3]n·nH2O (3), {[Eu2(3,5-pdc)3(H2O)3(CH3CHO)]n·n[2(H2O)(DMF)]} (4), {[Gd2(3,5-pdc)3 (H2O)2]n·2nH2O} (5) and [Er(3,5-pdc)(adip)0.5(H2O)]n (6) (where 3,5-pdc2- = fully deprotonated; 3,5-pdcH- = partially deprotonated 3,5-pyridinedicarboxylic acid; adip2- = fully deprotonated adipic acid; and DMF = dimethylformamide) by solvothermal self-assembly of lanthanide ions with rigid 3,5-pyridinedicarboxylic acid as a linker and adipic acid as an auxiliary flexible spacer (only coordinated in CP 6). CPs 1 and 2 crystallize in the triclinic P1[combining macron] space group, whereas CPs 3, 4 and 6 crystallize in the monoclinic P21/n, P21/c and C2/c space groups, respectively. CP 5 exhibits the trigonal R3 space group. The 3,5-pdc ligand exhibits eight diverse coordination modes in CPs 1-6, whereas the adipic acid spacer in CP 6 shows only one coordination mode (µ4-κO:κO,O:κO:κO,O). The organic ligands interconnect with metal ions to generate 3D metal-organic frameworks with a variety of intriguing topologies. Theoretical studies, DFT calculations and Hirshfeld surface analysis support the structures adopted by the various CPs. CPs 3 (Sm) and 4 (Eu) emit strong ligand-sensitized characteristic f-f luminescence. Weak ferromagnetic interactions have been studied at low temperatures for CP 1 and CP 5.
ABSTRACT
A terpyridine based compound L1 was designed and synthesized as an "off-on" chemosensor for the detection of Zn2+. Chemosensor L1 showed excellent selectivity and sensitivity toward Zn2+ by exhibiting a large fluorescence enhancement (â¼51-fold) at 370 nm whereas other competitive metal ions did not show any noticeable change in the emission spectra of chemosensor L1. The chemosensor (L1) was shown to detect Zn2+ ions down to 9.76 µM at pH 7.4. However, chemosensor L1 binds Zn2+ in a 1 : 2 ratio (receptor : metal) with an association constant of 1.85 × 104 (R2 = 0.993) and this 1 : 2 stoichiometric fashion is established on the basis of a Job plot and mass spectroscopy. DFT/TD-DFT calculations were carried out to understand the binding nature, coordination features and electronic properties of L1 and the L1-2Zn2+ complex. In addition, this "turn-on" fluorescence probe was effectively used to image intracellular Zn2+ ions in cultured MDA-MB-468 cells.
Subject(s)
Fluorescent Dyes/chemistry , Pyridines/chemistry , Zinc/analysis , Cell Line, Tumor , Cell Survival/drug effects , Fluorescent Dyes/toxicity , Humans , Ions/chemistry , Microscopy, Confocal , Models, Molecular , Pyridines/toxicity , Quantum Theory , Spectrophotometry, UltravioletABSTRACT
A new mononuclear tetra-hedral CoII complex, di-chlorido-bis-(imidazo[1,2-a]pyridine-κN1)cobalt(II), [CoCl2(C7H6N2)2], has been synthesized using a bioactive imidazo-pyridine ligand. X-ray crystallography reveals that the solid-state structure of the title complex exhibits both C-Hâ¯Cl and π-π stacking inter-actions in building supra-molecular assemblies. Indeed, the mol-ecules are linked by C-Hâ¯Cl inter-actions into a two-dimensional framework, with finite zero-dimensional dimeric units as building blocks, whereas π-π stacking plays a crucial role in building a supra-molecular layered network. An exhaustive investigation of the diverse inter-molecular inter-actions via Hirshfeld surface analysis enables contributions to the crystal packing of the title complex to be qu-anti-fied. The fingerprint plots associated with the Hirshfeld surface clearly display each significant inter-action involved in the structure, by qu-anti-fying them in an effective visual manner.
ABSTRACT
Two new Co(II) and Cu(II) coordination polymers, {Co(HL1)2(µ-L2)(H2O)2}n (1) and {[Cu(HL1)2(µ-L2)H2O]·H2O}n (2) (H2L1 = Phthalic acid and L2 = 2-aminopyrazine), have been synthesized by slow evaporation of solvent and characterized by IR spectroscopic, elemental, single-crystal X-ray diffraction and thermal analysis. X-ray results indicate that in both the polymers, phthalate acts as a monodentate ligand and the aminopyrazine ligand is responsible for the formation of the infinite one-dimensional chain structure. The solid-state structures are stabilized through hydrogen bonds and NâH···π interactions by generating two-dimensional layered structures. Finally, the non-covalent interactions have been studied energetically and using Bader's theory of atoms in molecules by means of Density Functional Theory (DFT) calculations. The influence of the metal coordination on the strength of the interaction has been studied using molecular electrostatic potential surface calculations.
ABSTRACT
Two novel Cu(II)-based metal-organic frameworks [C40H34Cu2N6O18 (1) and C20H18CuN2O10 (2)] have been synthesized using 2-aminopyrimidine or pyrazine ligands and phthalate ion and characterized spectroscopically and by X-ray single-crystal diffraction. Both 1 and 2 show electrical conductivity and photosensitivity, evidencing their potentiality in optoelectronic device applications. Experimental and theoretical investigations revealed that the electrical conductivity under irradiation of visible light increases compared to that under dark condition (photosensitive Schottky barrier diode behavior), especially in complex 2. Both 1 and 2 have been successfully applied in technologically challenging thin-film active devices.
ABSTRACT
Using ab initio calculations, we analyze the interplay between π-hole interactions involving the nitro group of 1,4-dinitrobenzene and lone pair···π (lp···π), C-H···π or metal(M)···π noncovalent interactions. Moreover, we have also used 1,4-phenylenebis(phosphine dioxide) for comparison purposes. Interesting cooperativity effects are found when π-hole (F···N,P) and lp···π/C-H···π/M···π interactions coexist in the same supramolecular assembly. These effects are studied theoretically in terms of energetic and geometric features of the complexes, which are computed by ab initio methods (RI-MP2/def2-TZVP). A charge density analysis using the Bader's theory of "atoms in molecules" is carried out to characterize the interactions and to analyze their strengthening or weakening depending on the variation of charge density at critical points. The importance of electrostatic effects on the mutual influence of the interaction is studied by means of molecular electrostatic potential calculations. By taking advantage of these computational tools, the present study examines interplay of these interactions. © 2017 Wiley Periodicals, Inc.
ABSTRACT
In this article, ab initio calculations have been combined with a search in the Protein Data Bank (PDB) to demonstrate the importance of σ-hole tetrel bonding interactions in biological systems. In particular, we focus our attention on the ability of the -CF3 group to participate in noncovalent interactions as Lewis acids, and we show the importance of this interaction in the inhibition mechanism of a NADP+-dependent isocitrate dehydrogenase (IDH) enzyme that converts isocitrate to α-ketoglutarate. IDH mutations are found in multiple hematologic and solid tumors, inducing premalignant disorders. A potent triazine-based inhibitor of the mutant IDH (enasidenib) presents two -CF3 groups in the structure. One establishes a tetrel bonding interaction with an aspartate residue that contributes to the binding and selectivity of the inhibitor to the active site.
ABSTRACT
In an unusual reaction of [Pd(L(1))Cl2] (L(1) = 2-(arylazo)pyridine) with amines, a new series of palladium complexes [Pd(L(2â¢-))Cl] (L(2) = 2-((2-amino)arylazo)pyridine) (1a-1h) were isolated. The complexes were formed via N-H and N-C bond cleavage reactions of 1°/2° and 3° amines, respectively, followed by regioselective aromatic ortho-C-N bond formation reaction and are associated with ortho-C-H/ortho-C-Cl bond activation. A large variety of amines including both aromatic and aliphatic were found to be effective in producing air-stable complexes. Identity of the resultant complexes was confirmed by their X-ray structure determination. Efforts were also made to understand the mechanism of the reaction. A series of experiments were performed, which point toward initial ligand reduction followed by intraligand electron transfer. Examination of the structural parameters of these complexes (1) indicates that the in situ generated ligand coordinated to the Pd(II) center serves as the backbone of these air-stable monoradical complexes. Molecular and electronic structures of the isolated complexes were further scrutinized by various spectroscopic techniques including cyclic voltammetry, variable temperature magnetic susceptibility measurements, electron paramagnetic resonance, and UV-vis spectroscopy. Finally the electronic structure was confirmed by density functional theory calculations. The isolated monoradical complexes adopt an unusual π-stacked array, which leads to a relatively strong antiferromagnetic interaction (J = -40 cm(-1) for the representative complex 1c).
ABSTRACT
Five M(II)-malonate complexes having a common formula (C(6)H(9)N(2))(4)[M(II)(C(3)H(2)O(4))(2)(H(2)O)(2)](PF(6))(2).(H(2)O)(2) (1-5) [where C(6)H(9)N(2) = protonated 3-picoline, M(II) = Ni/Co/Mn/Mg/Zn, C(3)H(4)O(4) = malonic acid, and PF(6)(-) = hexafluorophospahte], have been synthesized and their crystal structures have been determined. Complexes 1-5 were found to be isostructural and protonated 3-picoline has primarily mediated the self-assembly process. Role of a discrete water dimer in complexes 1-5 was also studied. Weaker π-interactions have also played crucial role in stabilizing 1D chain constructed by discrete [M(II)(C(3)H(2)O(4))(2)(H(2)O)(2)] units. An additional copper complex namely, (C(6)H(9)N(2))(4)[Cu(C(3)H(2)O(4))(2)](PF(6))(2) (6) has been synthesized from the same reagents and was found to have a completely different structure from the others. Structures of all the complexes are fully described and compared here. Moreover, the lone pair-π and π-π noncovalent interactions have been analyzed by means of DFT calculations, mainly focusing our attention to the influence of the coordinating metal on the strength of the interactions and the interplay between hydrogen bonding and π-interactions. We also present here Hirshfeld surface analysis to investigate the close intermolecular contacts.
ABSTRACT
A Cu(II)-malonate complex with formula {(C5H6N2Cl)12[Cu(1)(C3H2O4)2][Cu(2)(C3H2O4)2(H2O)2][Cu(4)(C3H2O4)2][Cu(3)(C3H2O4)2(H2O)2](ClO4)4}n (1) [C5H6N2Cl = protonated 2-amino-5-chloropyridine, C3H4O4 = malonic acid, ClO4(-) = perchlorate] has been synthesized from purely aqueous media simple by mixing the reactants in their stoichiometric ratio, and its crystal structure has been determined by single-crystal X-ray diffraction. In 1, copper(II) malonate units form infinite 1D polymeric chains, which are interlinked by hydrogen bonds to generate 2D sheets. These 2D sheets are joined side by side primarily by various hydrogen bonds to form a 3D structure. A multitude of salt bridges are formed in this structure, connecting the protonated 2-amino-5-chloropyridines and the malonate ligands of the polymeric polyanion. Examining this characteristic of the solid-state architecture, we noticed several salt-bridge (sb)···π interactions and an unexplored interaction between the lone pair (lp) of one malonate oxygen atom and a planar salt bridge. The combination of this interaction with various other weak intermolecular forces results in a remarkably extended supramolecular network combining a wide variety of interactions involving π-systems (Cl···π, π···π) and salt bridges (sb···π and lp···sb). We describe the energetic and geometric features of this lone pair-salt-bridge interaction and explore its impact on the resultant supramolecular organization using theoretical DFT-D3 calculations.
ABSTRACT
Keratitis treatment has become more complicated due to the emergence of bacterial or fungal pathogens with enhanced antibiotic resistance. The pharmaceutical applications of N-heterocyclic carbene complexes have received remarkable attention due to their antimicrobial properties. In this paper, the new precursor, 3,3'-(p-phenylenedimethylene) bis{1-(2- methyl-allyl)imidazolium} bromide (1a) and its analogous PF6 salt (1b) were synthesized. Furthermore, silver(I) and gold(I) -N-heterocyclic carbene (NHC) complexes [Ag2LBr2/Au2LBr2; 2a/3a], [(Ag2L2)(PF6)2/(Au2L2)(PF6)2; 2b/3b] were developed from their corresponding ligands. All compounds were screened for their antimicrobial activities against multiple keratitis-associated human eye pathogens, including bacteria and fungi. Complexes 2a and 3a showed highest activity, and the effectiveness of 3a was also studied, focusing eradication of pathogen biofilm. Furthermore, the structures of 1a, 2a and 3b were determined using single crystal X-ray analysis, 2b and 3a were optimized theoretically. The mechanism of action of 3a was evaluated by scanning electron microscopy and docking experiments, suggesting that its target is the cell membrane. In summary, 3a may be helpful in developing antimicrobial therapies in patients suffering from keratitis-associated eye infections caused by multidrug-resistant pathogens.
Subject(s)
Alkenes/pharmacology , Anti-Infective Agents/pharmacology , Biofilms , Eye Infections/drug therapy , Gold/pharmacology , Imidazoles/pharmacology , Keratitis/drug therapy , Alkenes/chemical synthesis , Alkenes/chemistry , Animals , Anti-Infective Agents/chemical synthesis , Anti-Infective Agents/chemistry , Cell Line, Tumor , Contact Lenses/microbiology , Contact Lenses, Extended-Wear , Eye Infections/etiology , Eye Infections/microbiology , Gold/chemistry , Humans , Imidazoles/chemistry , Keratitis/complications , Keratitis/microbiology , MiceABSTRACT
Three Co(II)-malonate complexes, namely, (C(5)H(7)N(2))(4)[Co(C(3)H(2)O(4))(2)(H(2)O)(2)](NO(3))(2) (1), (C(5)H(7)N(2))(4)[Co(C(3)H(2)O(4))(2)(H(2)O)(2)](ClO(4))(2) (2), and (C(5)H(7)N(2))(4)[Co(C(3)H(2)O(4))(2)(H(2)O)(2)](PF(6))(2) (3) [C(5)H(7)N(2) = protonated 2-aminopyridine, C(3)H(4)O(4) = malonic acid, NO(3)(-) = nitrate, ClO(4)(-) = perchlorate, PF(6)(-) = hexafluorophosphate], have been synthesized from purely aqueous media, and their crystal structures have been determined by single crystal X-ray diffraction. A thorough analysis of Hirshfeld surfaces and fingerprint plots facilitates a comparison of intermolecular interactions in 1-3, which are crucial in building supramolecular architectures. When these complexes are structurally compared with their previously reported analogous Ni(II) or Mg(II) compounds, a very interesting feature regarding the role of counteranions has emerged. This phenomenon can be best described as anion-induced formation of extended supramolecular networks of the type lone pair-π/π-π/π-anion-π/π-lone pair and lone pair-π/π-π/π-anion involving various weak forces like lone pair-π, π-π, and anion-π interactions. The strength of these π contacts has been estimated using DFT calculations (M06/6-31+G*), and the formation energy of the supramolecular networks has been also evaluated. The influence of the anion (NO(3)(-), ClO(4)(-), and PF(6)(-)) on the total interaction energy of the assembly is also studied.
ABSTRACT
The pi(+)-pi interactions are utilized to design the solid-state assembly of host-guest complexes where guests are anions. The doubly protonated MPTPH(2) (MPTP = 4'-(4-methoxyphenyl)-2,2':6',2''-terpyridine) complexed with H(2)O and Cl(-) or Br(-) are synthesized, crystallized, and characterized by X-ray analysis. By using the density functional theory calculations which can properly describe the dispersion energy, the assembling phenomena are analyzed in terms of pi(+)-pi and pi-pi interactions as well as H-bonding interactions. The planar structure of MPTPH(2)(Cl)(2).2H(2)O or MPTPH(2)(Br)(2).2H(2)O facilitates the crystal packing, since the pi(+)-pi interactions play an important role in the solid-state assembly.