Vincent J Smith

• Chemistry
• Rhodes University

A soft porous material [Zn(L)2(OH)2]n∙Guest (where L is 4-(1H-naphtho[2,3-d]imidazol-1-yl)benzoate, and Guest is water or methanol), exhibits the strongest ever observed negative area compressibility (NAC), an extremely rare property, as at hydrostatic pressure most materials shrink in all directions and few expand in one direction. This is the fir...

Two isoreticular 3D Cu(II)-glutarate based pillared-layered MOFs with flexible pillars, [Cu2(glu)2(bpa)] and [Cu2(glu)2(bpp)], undergo spontaneous phase changes upon solvent loss at room temperature. Using single-crystal X-ray diffraction analysis (SCXRD), we show that the phase changes result in new narrow-channel forms that experience a large red...

A novel three-dimensional metal-organic framework (MOF) that displays anisotropic thermal expansion has been prepared and characterized by single-crystal X-ray diffraction (SCD) and thermal analysis. The as-prepared MOF has one-dimensional channels containing guest molecules that can be removed and/or exchanged for other guest molecules in single-c...

A systematic study is presented of three closely related microporous metal-organic frameworks the pore dimensions of which vary according to the choice of 4,4′-bipyridyl linker. The tunable linker allows exploration of the effect of increasing pore dimensions on the sorption behavior of the frameworks. The MOFs described capture CO2 under supercrit...

A nitromethane solvate of 18-crown-6 was investigated by means of variable-temperature single-crystal X-ray diffraction in response to a report of abnormal unit cell contraction. Exceptionally large positive thermal expansion in two axial directions and negative thermal expansion along the third was confirmed. The underlying mechanism relies exclus...

A carboxylic acid, an aldehyde, and an isonitrile were combined in a single step (Passerini reaction) under mechanochemical activation to produce several α-acyloxycarboxamide derivatives in high to excellent yields within 15 min of milling. Mechanochemistry, when combined with the diversity provided by multicomponent reactions, enables the efficien...

A new simple, efficient, and environmentally friendly protocol is presented for the catalytic synthesis of α-acyloxycarboxamides using N-formamides as a carbonyl precursor under aqua and mechanochemical conditions. Immobilized sulfuric acid on silica gel was employed for the synthesis of desired products, via the reaction of benzoic acid, 1-napthyl...

A protocol based on the Passerini Multi‐Component reaction (MCR) has been developed for facile, efficient, environmentally benign and atom economical synthesis of a small library of biologically important oxindole derivatives employing isatin, benzoic acid and substituted isocyanides. In contrast to the conventional approach, which requires the use...

Spirocyclic scaffolds are found in many pharmacologically active natural and synthetic compounds. From time to time, efforts have been made to develop new or better processes for the synthesis of spirocyclic compounds. Spiro [Indole–pyrrolidine] Derivatives are readily synthesized in high to excellent yields by the Michael condensation of 3-dicyano...

A green and sustainable chemistry approach for organic synthesis is described here, which involves microwave exposure of reactants in the presence of water. A general, practical, and highly efficient protocol for the preparation of a broad range of functionalized isothiocyanates has been developed from their corresponding isocyanides using Lawesson...

A combined crystallographic and computational investigation reveals a turnstile mechanism for the gated uptake of C1–C4 alkanes in a seemingly nonporous MOF. In situ single-crystal X-ray diffraction reveals no significant structural change upon uptake of methane, while subnetwork displacement is induced by ethane uptake. Counterintuitively, only li...

The rare availability of suitable single‐crystal X‐ray diffraction (SCXRD) structural data allows for the direct interpretation of the response of a framework to gas sorption and may lead to the development of improved functional porous materials. We report an in situ SCXRD structural investigation of a flexible MOF subjected to methane, ethane, pr...

Currently, the human immunodeficiency virus (HIV) that causes acquired immunodeficiency syndrome (AIDS) can only be treated successfully, using combination antiretroviral (ARV) therapy. Lamivudine (3TC) and zidovudine (AZT), two compounds used for the treatment of HIV and prevention of disease progression to AIDS are used in such combinations. Succ...

Lamivudine (3TC) and zidovudine (AZT) are antiretroviral agents used to manage HIV/AIDS infection. A wet media milling top-down approach was used to develop and produce nano co-crystals of 3TC and AZT. Micro co-crystals were prepared by solvent evaporation and subsequently milled in the presence of two surfactants, viz., sodium lauryl sulfate (SLS)...

Crystals of organic salts can be grown by sublimation in two systems: succinic acid with hexamethylenetetramine, and oxalic acid with 4,4′-bipyridine. Both systems also form co-crystals by sublimation. Additionally, salts and co-crystals are able to re-sublime once formed, allowing the separation of different multicomponent crystal forms using subl...

Lamivudine (3TC) and zidovudine (AZT) are antiviral agents used to manage HIV/AIDS infection. The compounds require frequent dosing, exhibit unpredictable bioavailability and a side effect profile that includes hepato- and haema-toxicity. A novel pseudo one-solvent bottom-up approach and Design of Experiments using sodium dodecyl sulphate (SDS) and...

With an intention of identifying chalcone derivatives exhibiting anti-protozoal activity, a cohort of relatively unexplored arylpyrrole-based chalcone derivatives were synthesized in moderate to good yields. The resultant compounds were evaluated in vitro for their potential activity against a cultured Trypanosoma brucei brucei 427 strain. Several...

Lamivudine (3TC) and zidovudine (AZT) are antiviral agents used orally to manage HIV/AIDS infection. A pseudo one-solvent bottom-up approach was used to develop and produce nano co-crystals of 3TC and AZT. Equimolar amounts of 3TC dissolved in de-ionized water and AZT in methanol were rapidly injected into a pre-cooled vessel and sonicated at 4 °C....

A series of organic co-crystals has been prepared and structurally characterized. Consisting of p-benzoquinone (BQ) and one of four monosubstituted p-halophenols, co-crystals were made by crystallization from chloroform, co-sublimation in vacuo, and neat grinding. Co-crystals with both 1:1 and 2:1 donor-acceptor ratios can be prepared from all four...

Enthalpy of sorption (ΔH) is an important parameter for the design of separation processes using adsorptive materials. A pressure‐ramped calorimetric method is described and tested for the direct determination of ΔH values. Combining a heatflow thermogram with a single sorption isotherm enables the determination of ΔH as a function of loading. The...

Correction for ‘A combined stretching–tilting mechanism produces negative, zero and positive linear thermal expansion in a semi-flexible Cd( ii )-MOF’ by Prem Lama et al. , Chem. Commun. , 2014, 50 , 6464–6467.

Astute combination of basic functionality and luminescence property can pursue multifunctional metal-organic frameworks (MOFs) with assorted applications such as selective CO2 adsorption, specific detection of explosive nitro compounds and toxic metal ion sensing. The bifunctional ligand 4-(4-carboxyphenyl)-1,2,4-triazole (HL) is used to build the...

Crystals of 4-aminobenzonitrile grown by sublimation undergo reversible thermosalient phase changes during cooling and subsequent heating. Single-crystal diffraction studies have been carried out at 20 K intervals during cooling from...

4-bromobenzonitrile was crystallised by sublimation under vacuum. The crystals show highly flexible plastic bending along two perpendicular faces when a mechanical force is applied. The rare occurrence of bending along...

An organic cocrystal consisting of 4-aminobenzonitrile and 4-(dimethylamino)benzonitrile (ABN·2DMABN) undergoes positive linear thermal expansion along its three principal axes over the temperature range 100 – 300 K. The associated volumetric...

Novel, uncharged mixed-ligand [Pt(1,10-phenanthroline)(Ln-κS)2] (n = 1,2) complexes have been isolated, in which two usually chelating N,N-dibutyl-N’-1-naphthoyl-thioureato (L1)-, or N,N-diethyl-N’-benzoyl-thioureato (L2)- anions coordinate to Pt(phen)Cl2 in an unprecedented S-thio/amido mode of coordination. These compounds are previously unident...

Molecular recognition and hydrophobic effect explain the solvatomorphic behavior of a hexameric α-cyclic peptoid. Either a pure non-porous crystal form or a stable one-dimensional porous framework is obtained by appropriate...

The synthesis and characterization of a distally bridged, bidentate resorcinarene bis-carbene palladium complex is described for the first time. Preliminary catalytic studies show promise for future developments along this framework.

Metal-organic frameworks (MOFs) are an important class of porous materials with numerous potential applications. Molecular level understanding of various processes involving MOFs is very important in order to design porous materials with improved properties. Here we describe the elucidation by means of single-crystal X-ray diffraction (SCD) of thre...

It is demonstrated that guest replacement in a series of isoskeletal organic inclusion compounds can produce drastic changes in thermal expansion behavior. The compounds 1, 2 and 3 have 18-crown-6 as host molecule and nitromethane, acetonitrile and methyl iodide, respectively, as guests. Along the principle axis X1, the linear component of thermal...

A peptidomimetic compound undergoes a reversible single-crystal-to-single-crystal transformation upon guest release/uptake with the transformation involving a drastic conformational change. The extensive and reversible alteration in the solid state is connected to the formation of an unprecedented "CH-π zipper" which can reversibly open and close (...

The investigation of the solid state assembly of propargyl substituted hexa- and octacyclic peptoids highlights the effect of ring size in determining the packing arrangement of the macrocycles. A layered arrangement is obtained in the case of the hexacyclic peptoid 1 and a tubular arrangement in the case of the octacyclic peptoid 2. Guest molecule...

The interaction between the potent anticancer agent 2-methoxyestradiol (2ME) and a series of cyclodextrins (CDs) was investigated in the solid state using thermal analysis and X-ray diffraction, while the possibility of enhancing its poor aqueous solubility with CDs was probed by means of equilibrium solubility and dissolution rate measurements. Si...

7-Chloroquinoline-based antimalarial drugs are effective in the inhibition of hemozoin formation in the food vacuole of the Plasmodium parasite, the causative agent of malaria. We synthesized five series of ferroquine (FQ) and phenylequine (PQ) derivatives, which display good in vitro efficacy toward both the chloroquine-sensitive (CQS) NF54 (IC50...

Sublimation of p-iso-propylcalix[4]arene under reduced pressure results in the concomitant formation of two new polymorphs (forms IIP and IIIP). Both forms consist of interdigitated dimers of calixarene molecules, as does the known form IP. Despite similar inclusion behaviour to that of p-tert-butylcalix[4]arene, p-iso-propylcalix[4]arene does not...

A systematic study is presented of three closely related microporous metal-organic frameworks the pore dimensions of which vary according to the choice of 4,4′-bipyridyl linker. The tunable linker allows exploration of the effect of increasing pore dimensions on the sorption behavior of the frameworks. The MOFs described capture CO2 under supercrit...

The two previously reported solid state forms of p-cresol are revisited and detailed structural analysis, thermal analysis, lattice energy calculations and variable temperature powder X-ray diffraction are presented. A possible mechanism for the transformation from form II to form I is proposed.

Single crystals of a previously reported porous metallocycle [Ag2L2](BF4)2•2CH3CN (1), where L is the ligand 1,4-bis(2-methylimidazol-1-ylmethyl)benzene, were grown from acetonitrile and immersed in different organic solvents. The crystals thus treated were subjected to single-crystal X-ray diffraction analysis, which revealed that the acetonitrile...

A novel semi-flexible Cd(ii)-MOF has been synthesized and characterized by variable temperature powder and single-crystal X-ray diffraction. The material displays an unusual combination of thermal expansion (TE) i.e. negative, zero and positive, which is an extremely rare finding, especially for metal-organic frameworks as a result of a combined st...

A series of novel neutral and cationic methylpalladium complexes bearing N-alkyl-2,2′-dipyridylaldiminato ligands were prepared and characterized. In the presence of ethylene, the cationic complexes were active as dimerization catalysts, producing a mixture of 1- and 2-butenes. A Pd–ethyl π-ethylene species was identified as the catalyst resting st...

The sorption processes for hydrogen and carbon dioxide are of considerable, and growing interest, particularly due to their relevance to a society that seeks to replace fossil fuels with a more sustainable energy source. X-ray diffraction allows a unique perspective for studying structural modifications and reaction mechanisms that occur when gas a...

4-Phenoxyphenol crystallises to yield discrete ∼60 Å(3) cavities that are capable of enclathrating small solvent molecules; the cavities are capped by constricted 6-membered hydrogen-bonded rings and these potential apertures do not appear to facilitate gated porosity when the material is subjected to static CO2 pressure.

Offset-linked dimers of C-ethylpyrogallol[4]arene (PgC2) , 18-crown-6 have been synthesised and structurally elucidated. The 18-crown-6 acts as a template/guest for the assembly of the first observed tri-solvent-bridged, extended pyrogallol[4]arene-based dimers. Oppositely, adjacently and diagonally positioned macrocycles are connected through a co...

In the title compound, C21H20ClNO6, the furan moiety is located above the mean plane of the indole ring and displays rotational disorder (i.e. rotation through 180°); the site occupancy of the major component is 0.809 (6). In the crystal, C—H⋯O inter­actions link the mol­ecules into chains which run parallel to the b axis.

In the title compound, C21H20BrNO5S, the thio­phene group is located above the mean plane of the indole ring and displays rotational disorder (i.e. rotation through 180°). The site occupancy of the major component is 0.902 (2), while that of the minor component is 0.098 (2). In the crystal, pairs of weak C—H⋯O inter­actions link the mol­ecules into...

In the title compound, C15H12ClNO2S, the indole ring is essentially planar (r.m.s. deviation = 0.0107 Å) and makes a dihedral angle of 85.01 (6)° with the benzene ring. In the crystal, three C—H⋯O hydrogen bonds result in a hydrogen-bonded spiral running parallel to the c axis.

In the title compound, C18H18N4O4S2, the mean planes passing through the tosyl benzene rings form dihedral angles of 48.42 (9) and 15.1 (1)° with the amino­pyrimidine ring. In the crystal, mol­ecules associate via N—H⋯N and N—H⋯O hydrogen bonds, forming extended hydrogen-bonded sheets that lie parallel to the bc plane. The N—H⋯N hydrogen bonds prop...

In the title compound, C14H12N4, the dihedral angle between the indole ring system (r.m.s. deviation = 0.010 Å) and the imidazole ring is 77.70 (6)°. In the crystal, mol­ecules are linked by C—H⋯N hydrogen bonds. One set of hydrogen bonds forms an undulating chain running parallel to the b-axis direction, while the other undulating chain is paralle...

One pentacoordinated mononuclear complex [Zn(L)(NCS)]PF6 (1), one hexacoordinated 2D coordination polymer {[Cd2(L)(NCS)4]·0.24(CH3OH)}n (2) and one pentacoordinated 1D polymeric chain [Hg2(L)(SCN)4]n (3) [L = N,N′-(bis(pyridine-2-yl)benzylidene)-1,4-butanediamine] have been synthesized and X-ray crystallographically characterized. Structural analys...

The title compound, C19H19N3O4S2, was prepared by the reaction of 2,3-diamino­pyridine with tosyl chloride in a mixture of dichloro­methane–pyridine as solvent. In the crystal, mol­ecules associate via pairs of N—H⋯N hydrogen bonds, forming a centrosymmetric eight-membered {⋯HNCN}2 synthon. The dihedral angles between the amino­pyridine ring and th...

The concepts relating to the structures and properties of crystals involve numerous terms that might be especially bewildering to the nonspecialist. Many of these terms have been borrowed and/or adapted from mineralogy, a much older branch of crystallography and involving a different community of researchers, while others have been coined at will t...

An inclusion complex formation between α- and β-cyclodextrin and four phenylurea analogues, namely metobromuron, monolinuron, monuron and fenuron, is reported. Complex formation was established using solution 1H NMR spectroscopy. Complex stoichiometries were determined by the method of continuous variation using the chemically induced shifts of bot...

We report the formation of inclusion complexes between the phenylurea herbicide metobromuron [3-(p-bromophenyl)-1-methoxy-1-methylurea] and beta- and gamma-cyclodextrin in the solid state. Formation of crystalline inclusion complexes by the kneading method was confirmed by powder X-ray diffraction and further structural characterization using the p...

The E and Z isomers of the antithrombotic ajoene (4,5,9-trithiadodeca-1,6,11-triene 9-oxide), components of garlic ( Allium Sativa , L.), were complexed with heptakis(2,3,6-tri- O -methyl)--cyclodextrin (TRIMEB) to yield solid inclusion compounds with the compositions TRIMEB·( E )-ajoene·0.5H 2 O ( 1 ) and TRIMEB·( Z )-ajoene ( 2 ). These species w...