Huey Chong Kwong

Synthesis and Crystallographic Insight into the Structural Aspects of Some Novel Adamantane-Based Ester Derivatives

Adamantyl-based compounds are commercially important in the treatments for neurological conditions and type-2 diabetes, aside from their anti-viral abilities. Their values in drug design are chronicled as multi-dimensional. In the present study, a series of 2-(adamantan-1-yl)-2-oxoethyl benzoates, 2(a–q), and 2-(adamantan-1-yl)-2-oxoethyl 2-pyridinecarboxylate, 2r, were synthesized by reacting 1-adamantyl bromomethyl ketone with various carboxylic acids using potassium carbonate in dimethylformamide medium at room temperature. Three-dimensional structures studied using X-ray diffraction suggest that the adamantyl moiety can serve as an efficient building block to synthesize 2-oxopropyl benzoate derivatives with synclinal conformation with a looser-packed crystal packing system. Compounds 2a, 2b, 2f, 2g, 2i, 2j, 2m, 2n, 2o, 2q and 2r exhibit strong antioxidant activities in the hydrogen peroxide radical scavenging test. Furthermore, three compounds, 2p, 2q and 2r, show good anti-inflammatory activities in the evaluation of albumin denaturation.

The crystal structure of zwitterionic 2-{[(4-imin­iumyl-3-methyl-1,4-di­hydro­pyridin-1-yl)meth­yl]carbamo­yl}benzoate hemihydrate

The molecular and crystal structure of zwitterionic 2-{[(4-iminiumyl-3-methyl-1,4-dihydropyridin-1-yl)methyl]carbamoyl}benzoate hemihydrate is reported. The crystal structure is stabilized by a variety of hydrogen bonds and offset π–π stacking interactions.

Crystal structure of 4-({(1E,2E)-3-[3-(4-fluoro-phen-yl)-1-isopropyl-1H-indol-2-yl]allyl-idene}amino)-1H-1,2,4-triazole-5(4H)-thione.

The asymmetric unit of the title compound comprises two independent molecules which exist in the trans conformation with respect to the methene C= C and the acyclic N=C bonds. In the crystal, molecules are linked via N—H⋯N hydrogen bonds, forming chains along the b-axis direction.

Radical scavenging potency of 2-(benzofuran-2-yl)-2-oxoethyl 3-(methyl/amino)benzoate: synthesis, crystal structure and Hirshfeld surface analysis

Abstract Two novel 2-(benzofuran-2-yl)-2-oxoethyl 3-(methyl/amino)benzoates 2(a–b), were synthesized under mild conditions and characterized by spectroscopic analysis. The three-dimensional (3D) crystal structures of these compounds were further determined using single crystal X-ray diffraction technique and revealed that both compounds tend to twist away with respect to their attached carbonyl groups at the C(=O)–C–O–C(=O) connecting bridge, exhibiting a nearly perpendicular conformation with torsion angle in a range of 75–94°. In both compounds, each of the benzofuran and substituted phenyl rings are individually planar while almost perpendicular to each other. Their molecular conformation are comparable with related structures from the Cambridge Structural Database (CSD). Furthermore, the intermolecular interactions in these crystal structures were quantified and analyzed using Hirshfeld surfaces computational method. The quantitative data on the percentage contributions of overall interactions on the molecules 2a and 2b (A & B) is calculated by the 2-D fingerprint plots from the HS analysis. These structures were evaluated for their antioxidant properties by diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, ferrous ion chelating (FIC) and hydrogen peroxide radical scavenging assays (H2O2). Noteworthy, compound 2b with an amino substituent attached to the phenyl ring exhibited an IC50 value of 45.37 μg/mL in H2O2 scavenging assay, which showed better scavenging effect than the standard drug, ascorbic acid (IC50=81.02 μg/mL).

Tyrosinase inhibition potency of phthalimide derivatives: crystal structure, Hirshfeld surface analysis and molecular docking studies

Abstract A new series of seven 2-((pyridinylamino)methyl)isoindoline-1,3-dione derivatives were synthesized under mild condition and characterized by spectroscopy analysis. The crystal structures of these derivatives were further determined using single crystal X-ray diffraction technique. All derivatives adopt a V-shape conformation. The dihedral angle between phthalimide and pyridine rings increases as the torsion angle C1–N1–C9–N2 between phthalimide ring and methylene group increases. The torsion angles and molecular conformations are comparable to those related structures from the Cambridge Structural Database (CSD). Furthermore, the intermolecular interactions of all studied crystal structures were quantified and analyzed using Hirshfeld surface (HS) analysis. The quantitative data on the percentage contributions of overall interactions in all compounds are calculated by the two-dimensional (2D) fingerprint plots from the HS analysis. These compounds were evaluated for their antioxidant and antityrosinase properties. Noteworthy, 2-(((6-methoxypyridin-3-yl)amino)methyl)isoindoline-1,3-dione (compound g) exhibited higher tyrosinase inhibitory activity (EC50=753 μg/mL) than the positive control ‘arbutin’ (EC50=403 μg/mL). The inhibitory effect of compound g was further confirmed by computational molecular docking studies and the result revealed the 6-methoxypyridin-3-yl substituent has a better binding affinity toward tyrosinase.

6,6′-[(1E,1′E)-Oxybis(4,1-phenyl­ene)bis­(aza­nylyl­idene)bis­(methanylyl­idene)]bis­(2-methyl­phenol): supra­molecular assemblies in two dimensions mediated by weak C—H⋯N, C—H⋯O and C—H⋯π inter­actions

The title compound is a flexible Schiff base, as illustrated by its dihedral angles. The sp 2-hybridized character of the azanylylidene groups is confirmed by their bond lengths and bond angles. In the crystal, molecules of the title compound are assembled into two-dimensional networks connected by weak C—H⋯O, C—H⋯N and C—H⋯π intermolecular interactions.

Synthesis, spectroscopic and Hirshfeld surface analysis and fluorescence studies of (2E,2′E)-3,3′-(1,4-phenyl­ene)bis­[1-(4-hy­droxy­phen­yl)prop-2-en-1-one] N,N-di­methyl­formamide disolvate

In the bischalcone molecule, the central benzene and terminal hydroxyphenyl rings form a dihedral angle of 14.28 (11)° and the central C=C double bond adopts a trans conformation. In the crystal, the title molecule and solvate are linked by O—H⋯O hydrogen bonds.

Structure–property relation and third-order nonlinear optical studies of two new halogenated chalcones

Abstract In the present work, the crystal structure and third-order nonlinear optical (NLO) properties of two novel chalcone derivatives namely (E)-3-(4-bromo-2-fluorophenyl)-1-(3,4-dimethoxyphenyl)prop-2-en-1-one (I) and (E)-3-(4-bromophenyl)-1-(3,4-dimethoxyphenyl)prop-2-en-1-one (II) are investigated by analyzing the packing pattern, intermolecular interaction, Hirshfeld surface analysis and standard Z-scan technique with continuous wave laser at 532 nm. Both compounds are donor-acceptor-acceptor (D–A–A) type intramolecular charge transferring molecule which crystallized in centrosymmetric space group. The existence of C–H···O hydrogen bonds in I and Br···O short contact interactions in II play important roles in their packing pattern and NLO properties. The molecules reveal a strong nonlinear refraction (NLR) and nonlinear susceptibility χ(3) when the donor and acceptor are arranged side-by-side as in compound I. And as the donor and acceptor are aligned on a head-to-head alignment, the molecules divulge a strong third-order nonlinear absorption (NLA) and limiting threshold (LT). The Z-scan results indicate that both compounds would be potential applicants in the development of NLO devices.

Two closely related 2-(benzofuran-2-yl)-2-oxoethyl benzoates: structural differences and C—H...O hydrogen-bonded supramolecular assemblies

The title compounds contain a benzofuran ring and an ortho-substituted phenyl ring connected by a carbonyl bridge. The molecular conformations of both compounds are similar, but differ in the torsion angles between the ortho-substituted phenyl ring and its adjacent carbonyl group. The crystal structures feature C—H⋯O hydrogen bonds.

Steric repulsion and supra­molecular assemblies via a two-dimensional plate by C—H⋯O hydrogen bonds in two closely related 2-(benzo­furan-2-yl)-2-oxoethyl benzoates

The title compounds are constructed from a benzofuran ring and an ortho-substituted phenyl ring connected by a carbonyl-connecting bridge. The structural conformation of the compounds are under substantial influence of steric repulsion. In the crystals, the molecules are connected by C—H⋯O hydrogen bonds and π–π interactions [with extra C—H⋯π interaction for compound (II)].