Matthew Akerman

University of KwaZulu-Natal | ukzn · School of Chemistry and Physics

Controlled sulfonyl migration is considered an important transformation for total synthesis, and scaffold elaboration. Accordingly, efforts to understand the underlying properties of these often serendipitously identified reactions have important implications. Following the attempted synthesis of a tetrahydroindazolone analogue, we report here an u...

Three bis(pyridyl-imine) ligands 1,2-bis(2-pyridylaminomethyl)benzene (L1), 1,3-bis(2- pyridylaminomethyl)benzene (L2) and 1,4-bis(2-pyridylaminomethyl)benzene (L3) were synthesised and complexed to silver(I) salts forming four novel complexes; 1,2-bis(2-pyridylaminomethyl)benzene-silver(I) hexafluoroantimonate(V) [Ag(L1)](SbF6), bis(1,3-bis(2-pyri...

A series of Fe(III), Co(III), Ni(II), Cu(II), Zn(II) and In(III) N-morpholine-N'-benzoylthiourea complexes have been synthesised and characterised by elemental analysis, thermal analysis, infrared spectroscopy, 1H nuclear magnetic resonance spectroscopy and single crystal X-ray crystallography. Thermogravimetric analysis shows that all the complexe...

Three imidazole-derived Schiff base compounds comprising an N -methyl imidazole group coupled to a phenol ring through an imine bond were synthesised. The solid state and solution state supramolecular structures as well as energetics are explored.

In this study, we investigated a series of triarylimidazoles, in an effort to elucidate critical SAR information pertaining to their anti-plasmodial and β-hematin inhibitory activity. Our results showed that in addition to the positional effects of ring substitution, subtle changes to lipophilicity and imidazole ionisability were important factors...

(Pyrazolyethyl)pyridine palladium (II)complexes have been structurally characterized and found to give active catalysts in themethoxycarbonylation of higher olefins to mainly linear esters. The catalyticactivities of the complexes were mainly controlled by nature of the acidpromotor, phosphine derivative and olefin chain length. DFT studies establi...

A distorted single crystal structure of bis(piperidinedithiocarbamato)lead(II) complex and its subsequent use to deposit thin films is reported. Two deposition routes namely, aerosol-assisted chemical vapour deposition (AACVD) and spin coating deposition have been employed to obtain anisotropic lead sulfide (PbS) nanostructures. The thin films disp...

Herein, we report the DNA interaction studies of rhenium(I) and -(V) compounds with Schiff base chelates encompassing biologically relevant moieties. More specifically, the DNA interaction capabilities of these rhenium complexes were probed using Gel Electrophoresis and Calf Thymus–DNA titrations monitored by temperature-controlled electronic spect...

The development of cost effective and easily accessible bifunctional materials, which can be effectively used for energy storage and energy generation is highly desirable. Herein, a new molecular precursor [tris(morpholinodithiocarbamato)Co(III)] has been synthesized and the X‐ray crystal structure of the complex determined. The precursor was used...

Two heterocyclic dithiocarbamate complexes, tris-(piperidinedithiocarbamato)bismuth(III) (1) and tris-(tetrahydroquinolinedithiocarbamato)bismuth(III) (2) were synthesized and characterized by elemental analysis and thermogravimetric analysis. The structure of complex (1) was confirmed by single-crystal X-ray analysis. Both complexes were used as s...

Herein, we report the formation and characterisation of novel rhenium(I) and -(V) compounds with coumarin bidentate chelates: trans-[ReOBr2(PPh3)(hbc)] (1) (Hhbc = 7-(2-hydroxybenzylideneamino)-4-(trifluoromethyl)-2H-chromen-2-one), fac-[Re(CO)3Cl(aomc)] (2) (aomc = 7-(((2-amino-4-oxo-4H-chromen-3-yl)methylene)amino)-4-(trifluoromethyl)-2H-chromen-...

The lead N’-benzoylthioureato complexes of N-morpholine (1) and N-pyrrolidine (2) were synthesized and characterized by elemental analysis, Fourier Transform Infra-Red (FT-IR) spectroscopy, proton nuclear magnetic resonance (¹H nmr) and thermogravimetric analyses (TGA). The X-ray single crystal structure of complex (1) was determined. The compounds...

The bis(N'-ethyl-N-piperazinylcarbodithioato-S,S')-nickel(II) complex was prepared and characterized by infrared spectroscopy, thermogravimetric and elemental analyser. The crystal X-ray structure for bis(N'-ethyl-N-piperazinylcarbodithioato-S,S')-nickel(II) was determined. The complex was subsequently used as a single source precursor (SSP) for th...

Owing to their bioactivity and prevalence in medicinal plant extracts, prenylated phloroglucinols have garnered significant interest. Towards the synthesis of prenylated phloroglucinol derivatives, 2,4,6-trihydroxy-3-(3-methylbut-2-enyl)acetophenone is required as an intermediate. Herein, this was synthesised by a tandem Claisen-Cope rearrangement...

In this research study, the formation of new rhenium(III) and –(V) complexes with multidentate lumazine Schiff bases with carbohydrazide moieties: cis-[ReOBr2(PPh3)(bzlm) (1) (Hbzlm = N’-(1-(1,2,3,4-tetrahydro-1,3,7-trimethyl-2,4-dioxopteridin-6-yl)ethylidene)benzohydrazide) and cis-[ReBr2(PPh3)(tplm) (2) (tplm = N’-(1-(1,2,3,4-tetrahydro-1,3,7-tri...

Herein, we explore the coordination behaviours of Schiff bases derived from constituents of essential oils (viz. cinnamaldehyde and cuminaldehyde) and aromatic amines (viz. 2-aminophenol and 4-aminoantipyrene) towards the facial tricarbonylrhenium(I) core. The resultant rhenium(I) compounds: (µ-X)2[Re(CO)3]2 {where X = 2-{[3-phenylprop-2-en-1-ylide...

Mycobacterium tuberculosis (Mtb) and the fast-growingMycobacterium abscessus(Mab) are two important human pathogens causing persistent pulmonary infections that are difficult to cure and require long treatment times. The emergence of drug resistantMtbstrains and the high level of intrinsic resistance ofMabcalls for novel drug scaffolds that effecti...

The respective coordination reactions of trans-[ReOCl3(PPh3)2] with N-[(4-oxo-4H-chromen-3-yl)methylidene]thiophene-2-carbohydrazide (Hchrtc) and N-[1,3-benzothiazol-2-ylmethylidene]thiophene-2-carbohydrazide (Hbztc) afforded two novel oxorhenium(V) complexes, cis-[ReOCl2(chrtc)(PPh3)] (1) and cis-[ReOCl2(bztc)(PPh3)] (2). These metal compounds wer...

We report the syntheses of Zn (II) thiosemicarbazone complexes, ZnCl2(benztsczH)2(1), Zn(benztscz)2(2) and Zn(4-Cl-benztscz)2 (3), where (benztscz = benzaldehyde thiosemicarbazone (L1) and 4-Cl-benztscz = 4-Chloro benzaldehyde thiosemicarbazone (L2)). The complexes were used as single source precursors for the fabrication of ZnS nanoparticles via t...

A series of dialkyl 2,2’-disulfanediyldibenzoates with alkyl chain length C8 to C12 were synthesized and characterized by spectral studies. The structure of compound 3 was also confirmed by X-ray crystallography. The compounds were found to possess good antibacterial activity, especially with respect to Gram positive bacteria, and the activity was...

Novel facial tricarbonylrhenium(I) complexes, fac-[Re(urca)2(CO)3Cl] aR. Schibli, P.A. Schubiger, Eur. J. Nucl. Med. Mol. Imaging, 29 (2002) and fac-[Re(bzta)(CO)3Cl] Dilworth and Parott (1998) were isolated from the coordination reactions of 5-((5-hydroxypentylimino)methyl)uracil (urca) and 2-((5-hydroxypentylimino)methyl)benzothiazole (bzta) with...

Herein, we report the synthesis, characterization and DNA binding studies of novel rhenium(I) and (V) complexes with Schiff bases derived from 4-aminotetrahydropyran. More specifically, the coordination reactions of 2-((tetrahydro-2H-pyran-4-ylimino)methyl)phenol (Htmp) with trans-[ReOCl3(PPh3)2], trans-[ReOBr3(PPh3)2] and cis-[ReO2I(PPh3)2] afford...

In this research study, the formation of rhenium(I) complexes with bidentate carbohydrazide Schiff bases are reported. More specifically, the respective coordination reactions of [Re(CO)5Cl] with N-[1,3-benzothiazol-2-ylmethylidene]pyridine-2-carbohydrazide (bzpc), N-[1,3-benzothiazol-2-ylmethylidene]thiophene-2-carbohydrazide (bztc) and N-[(4-oxo-...

Two facial tricarbonylrhenium(I) compounds, fac-[Re(CO)3(urterpy)].NO3 (1) (urterpy = 4′-(5-(uracil-5-methyleneamino)pentanoxy)-2,2′:6′,2″-terpyridine) and fac-[Re2(CO)6(μ-bzterpy)Cl2] (2) (bzterpy = 4′-(5-(benzothiazole-2-methyleneamino)pentanoxy)-2,2′:6′,2″-terpyridine) were isolated and characterized by IR, NMR, UV-Vis and emission spectroscopy....

A series of single-chained N-acyl tyrosine surfactants with varying chain lengths (C10-C18) and degree of unsaturation, as well as an N-acyl Gemini tyrosine surfactant with chain length C12, were synthesized, and the structures were confirmed using spectral analysis. The effect of chain length and level of unsaturation on the physicochemical and an...

A novel tetradentate dipyrrolidequinoxaline ligand, 5-(3-{5-[(E)-(propylimino)methyl]-1H-pyrrol-2-yl}quinoxaline-2-yl)-1H-pyrrole-2-carbaldehyde (H2L1) and its Ni(II) complex, 2-[3-(5-formyl-1H-pyrrol-2-yl)quinoxaline-2-yl]-5-(prpylimino)methyl]propyl-1-ide nickel(II), [Ni(L1)], have been synthesised and studied by X-ray crystallography. The asymme...

Two nickel(II) complexes, namely piperidine (1) and tetrahydroquinoline (2) dithiocarbamate complexes were synthesized and characterized by infra-red spectroscopy, elemental analysis and thermogravimetric analyses. The single crystal X-ray structure of complex (1) was also elucidated. The as-synthesized complexes have been utilized as single source...

In this research study, the formation and characterization of new ruthenium(II) and (III) complexes encompassing multidentate ligands derived from 6-acetyl-1,3,7-trimethyllumazine (almz) are reported. The 1:1 molar coordination reactions of trans-[RuCl2(PPh3)3] with N-1-[1,3,7-trimethyllumazine]benzohydride (bzlmz) and 6-(N-methyloxime)-1,3,7-trime...

This paper describes the synthesis of (pyridyl)benzoazole Zn(II) and Cu(II) complexes and their applications as catalysts in ring-opening polymerization (ROP) of ε-caprolactone (ε-CL). Reactions of 2-(3-pyridyl)-1H-benzimidazole (L1), 2-(2-pyridyl)-1H-benzothiazole (L2) and 2-(2-pyridyl)-1H-benzimidazole (L3) with Zn(II) and Cu(II) acetates produce...

Four bis(pyrazolyl)pyridine Zn(II) and Cu(II) carboxylate complexes have been structurally elucidated and used as initiators in the ring-opening polymerization (ROP) of ε-carprolactone (ε-CL). Reactions of bis(3,5-dimethyl-pyrazol-1-yl)pyridine (L1) with the appropriate Zn(II) and Cu(II) carboxylates afforded the corresponding complexes; [Zn(L1)(C6...

In this research study, the coordination behaviours of perimidine ligands incorporating fused N-donor heterocyclics towards rhenium in its oxidation states +I and +V are explored. The equimolar coordination reactions of 2-(benzothiazole)-2,3-dihydro-1H-perimidine (bzpm) and 2,3-dihydro-2-(pyridine)-1H-perimidine (H2pypm) with [Re(CO)5Br] afforded t...

Herein, we explore the coordination of di- and triimine chelators at ruthenium(II) and ruthenium(III) centers. The reactions of 2,6-bis-((4-tetrahydropyranimino)methyl)pyridine (thppy), N1,N2-bis((3-chromone)methylene)benzene-1,2-diamine (chb), and tris-((1H-pyrrol-2-ylmethylene)ethane)amine (H3pym) with trans-[RuIICl2(PPh3)3] afforded the diamagne...

Reactions of (2-(2-pyridyl)benzimidazole (L1), 2-(2-pyridyl)benzothiazole (L2) and 2-(2-pyridyl)benzoxazole (L3) with either [PdCl2(NCMe)2] or [PdClMe(COD)] produced complexes [(PdCl2(L1)] (1), [(PdCl2(L2)] (2), [(PdCl2(L3)] (3) and [(PdClMe(L1)] (4) in good yields. Treatment of 1 with PPh3 gave the cationic complex [(Pd(L1)ClPPh3]Cl (5), while rea...

The application of transition metal chelates as chemotherapeutic agents has the advantage that they can be used as a scaffold around which ligands with DNA recognition elements can be anchored. The facile substitution of these components allows for the DNA recognition and binding properties of the metal chelates to be tuned. Copper is a particularl...

Reductions of imine compounds 2-methoxy-N-(1-(pyridin-2-yl)ethylidene)ethanamine (L1), 2-methoxy-N-((pyridin-2-yl)methylene)ethanamine (L2), N,N-diethyl-N-((pyridin-2-yl)methylene)ethane-1,2-diamine (L3) and 2-((pyridin-2-yl)methyleneamino)ethanol (L4) using NABH4 produced their corresponding amine analogues N-(2-methoxyethyl)-1-(pyridin-2-yl)ethan...

We report the synthesis, molecular structures and applications of bis(pyrazolylmethyl)pyridine Zn(II) and Cu(II) complexes in the ring-opening polymerization (ROP) of ε-carprolactone (ε-CL). Reactions of bis(3,5-dimethyl-pyrazol-1-ylmethyl)pyridine (L1) with the appropriate Zn(II) and Cu(II) carboxylates afforded the corresponding complexes; [Zn(L1...

The (imino)pyridine ligands bearing pendant arms 2-methoxy-N-(1-(pyridin-2-yl)ethylidene)ethanamine (L1), 2-methoxy-N-((pyridin-2-yl)methylene)ethanamine (L2), 3-methoxy-N-((pyridin-2-yl)methylene)propan-1-amine (L3), N,N-diethyl-N-((pyridin-2-yl)methylene)ethane-1,2-diamine (L4), and N-((6-bromopyridin-2-yl)methylene)-2-methoxyethanamine (L5) were...

Herein, we communicate the synthesis of a novel rhenium(I) complex, fac-[Re(CO) 3 (chrpychr)Br] (1) from the equimolar reaction between 2-(4-oxo-4H-chromen-3-yl)-5H-chromeno[2,3-d]pyrimidin-5-one (chrpychr) and [Re(CO) 5 Br]. The metal complex 1 was characterized via 1 H NMR-, IR-and UV–Vis spectroscopy and conductivity measurements. Single crystal...

Reactions of N-(1H-benzoimidazol-2-ylmethyl)-2-methoxy aniline (L1) and N-(1H-benzoimidazol-2-ylmethyl)-2-bromo aniline (L2) with either [PdCl2(COD)] or [PdClMe(COD)] afforded the neutral palladium complexes [PdCl2(L1)] (1), [PdClMe(L1)] (2) and [PdClMe(L2] (3), respectively. Treatment of 2 and 3 with one equivalent of PPh3 in the presence of NaBAr...

Two nominally square planar palladium(II) chelates: dichloro-(2-aminomethylpyridine-N,N′)-palladium(II) ([Pd(L1)Cl2]) and dichloro-(8-aminoquinoline)-palladium(II) ([Pd(L2)Cl2]) have been synthesised and studied by X-ray crystallography and DFT methods. [Pd(L1)Cl2] crystallised in the monoclinic space group C2/c. In the solid state this compound ex...

Herein, we report the isolation of ruthenium(II/III) compounds with N,O-donor heterocyclic ligands. The 1:2 molar ratio reactions of trans-[RuCl2(PPh3)3] with 2-hydroxyphenylbenzimidazole (Hobz) and 2-hydroxyphenylbenzothiazole (Hobs), respectively, led to the formation of the diamagnetic ruthenium(II) complex salt, [RuCl(Hobz)2(PPh3)]Cl(1) and the...

Cobalt and iron phthalocyanines (Pcs) bearing peripherally tetra-substituted chromone (chr) or coumarin (cou) moieties were formulated and characterized by UV–Vis and FTIR spectroscopy, ESI-TOF mass spectrometry, and elemental analysis. The structural elucidations of the ligands, 4-(chromone-7-oxy) phthalonitrile (1) and 4-(4-(trifluoromethyl)-coum...

A series of quaternary ammonium compounds (QUATS) derived from L-Phenylalanine have been synthesized and their antibacterial efficiencies were determined against various strains of Gram-positive and Gram-negative bacteria. The antibacterial activity increased with increasing chain length, exhibiting a cut-off effect at C14 for Gram-positive and C12...

In this account, we report the isolation of novel vanadium(IV) and -(V) compounds with 2-substituted phenyl/pyridyl heterocyclic chelates. The 1:2 molar reaction between NH4VO3 and 2-hydroxyphenylbenzothiazole (Hobs) led to the formation of a polynuclear vanadium(IV) compound, [VO(obs)(2)](n) (1). A trigonal bipyramidal mononuclear complex, cis-[VO...

Reactions of 2-bromo-6-(3,5-dimethyl-1H-pyrazol-1-yl)pyridine (L1) and 2,6-bis(3,5-dimethyl-1H-pyrazol-1-yl)pyridine (L2) with NiCl2 and NiBr2 led to the formation of their respective metal complexes [NiCl2(L1)] (1), [NiBr2(L1)] (2) and [NiBr2(L2)] (3) in moderate to high yields. The complexes were characterized using elemental analyses, mass spect...

Reactions of 2-(chloromethyl)-6((3,5-dimethyl-1H-pyrazol-1-yl)methyl)pyridine (L1) and 2-(chloromethyl)-6-((3,5-diphenyl-1H-pyrazol-1-yl)methyl)pyridine (L2) with NiCl2, NiBr2, CoCl2 and FeCl2 led to the formation of their respective metal complexes [NiCl2(L1)] (1), [NiBr2(L1)] (2), [CoCl2(L1)] (3), [FeCl2(L1)] (4), [NiBr2(L2)] (5), and [CoCl2(L2)1...

The title compound, [CoCl2(C15H12N2)2]·0.5CH2Cl2, was crystallized from a binary mixture of dichloromethane and hexane and a dimeric supramolecular structure was isolated. The CoII centre exhibits a distorted tetrahedral geometry, with two independent pyrazole-based ligands occupying two coordination sites and two chloride ligands occupying the thi...

Topoisomerase IB (Top1) is a key eukaryotic nuclear enzyme that regulates the topology of DNA during replication and gene transcription. Anticancer drugs that block Top1 are either well-characterized interfacial poisons or lesser-known catalytic inhibitor compounds. Here we describe a new class of cytotoxic redox-stable cationic Au(3+) macrocycles...

Three pyrrolide-imine Schiff base compounds: 1-phenyl-N-[(E)-1H-pyrrol-2-ylmethylidene]methanamine (1), 2-phenyl-N-(1H-pyrrol-2-ylmethylidene)ethanamine (2) and 1-(naphthalen-1-yl)-N-[(E)-1H-pyrrol-2-ylmethylidene]methanamine (3) have been synthesized in this work. The compounds were all synthesized via solid-state reactions which proved to be a ra...

Herein, we describe the coordination behavior of chromone Schiff bases towards [Re(V)O]3+ and [Re(I)(CO)3]+. The reaction between 2-(2-thiolphenyliminomethyl)-4H-chromen-4-one (Htch) and [Re(CO)5Cl] led to fac-[Re(CO)3(bsch)Cl] (1) (bsch = 2-benzothiazole-4H-chromen-4-one). The square pyramidal [ReO(Hns)] (2) {H2ns = bis-[(2-phenylthiolate)iminomet...

The synthesis and structural characterization of ruthenium complexes supported by 2-(2-pyridyl)benzoazole ligands and their evaluation as catalysts in the transfer hydrogenation of ketones are reported. Reactions of 2-(2-pyridyl)benzoimidazole (), 2-(2-pyridyl)benzothiazole () and 2-(2-pyridyl)benzoxazole () with RuCl3·3H2O produced the correspondi...

Herein we report the synthesis and characterization of trans-[RuII Cl2(PPh3)3] with potentially tridentate Schiff bases derived from 5,6-diamino-1,3-dimethyl uracil (H2ddd) and two 2-substituted aromatic aldehydes. In the diamagnetic ruthenium(II) complexes, trans-[RuCl(PPh3)2(Htdp)] (1) {H2tdp = 5-((thiophen-3-yl)methyleneamino)-6-amino-1,3-dimeth...

The biodistribution of an N2 N2 ' tetradentate gold(III) chelate, which is known to be cytotoxic towards a range of human cancer cell lines, was determined by a radiolabelled equivalent of the compound. The (198) Au-labelled gold(III) chelate of a bis(pyrrolide-imine) Schiff base ligand with a three-carbon di(azomethine) linkage was successfully sy...

The coordination behaviour of Hpybz (2-pyridylbenzimidazole) towards vanadium in various oxidation states (i.e. +III/IV/V) has been explored. The six-coordinate complex cis-[VVO2(Hpybz)(pybz)] (1) was isolated as the CH3OH·(H2O)2 hydrate from the reaction of NH4VO3 and Hpybz in aqueous methanol. The crystal structure shows that vanadium is bonded t...

In the title co-crystal, C(12)H(12)N(6)O(4)·C(14)H(16)N(4)O(2)S, both mol-ecules are essentially planar [maximum deviations = 0.129 (1) and 0.097 (1) Å, respectively]. The tricyclic and Schiff base mol-ecules are alternately stacked along the a axis and are linked by π-π inter-actions with centroid-centroid distances of 3.5170 (16) and 3.6576 (17) ...

The title compound, C(32)H(24)N(6)O(2), has an inversion centre located at the mid-point of the central C-C bond of the diether bridging unit. The terminal pyridine rings are canted relative to the central pyridine ring, with dihedral angles of 12.98 (6) and 26.80 (6)°. The maximum deviation from the eight-atom mean plane, defined by the two bridgi...

In the title thiophene-derived Schiff base compound, C 12 H 8 N 2 S 2 , the thiophene ring is slighty rotated from the benzothiazole group mean plane, giving a dihedral angle of 12.87 (6)°. The largest displacement of an atom in the molecule from the nine-atom mean plane defined by the non-H atoms of the benzothiazole ring system is 0.572 (1) Å, ex...

The reaction between cis-[Re V O 2 I(PPh 3) 2 ] and H 3 duo (N-(2-hydroxybenzylidene)-5-amino-1,3-dimethyl uracil) led to the formation of the oxofree, imido compound, trans-[Re V (ddd)(Hduo)(PPh 3) 2 ]I (1) (H 2 ddd = 5,6-diamino-1,3-dimethyluracil). An oxo complex, cis-[Re V (bcp)OCl 2 (PPh 3)](2) [Hbcp = N-(2-hydroxybenzylidene)-benzothiazole] w...

The pyridine rings of the title compound, C(18)H(23)N(3), are in a nearly perpendicular orientation relative to the plane defined by the three amino-bonded C atoms, making dihedral angles of 87.4 (1) ° and 84.2 (1) °. One of the pyridine N atoms acts as an hydrogen-bond acceptor for two pyridine C-H groups. By means of these intermolecular hydrogen...

The title compound, C(13)H(13)BN(2)O, is one in a series of 1,3,2-benzodiaza-boroles featuring a 2-meth-oxy-phenyl substitution at the 2-position in the nitro-gen-boron heterocyle. The dihedral angle between the mean planes of the benzodiaza-borole and 2-meth-oxy-phenyl ring systems is 21.5 (1)°. There is an inter-molecular hydrogen bond between on...

The mol-ecule of the title compound, C(36)H(32)N(6)O(2), lies about an inversion center, located at the mid-point of the central C-C bond of the diether bridge. The terminal pyridine rings form dihedral angles of 4.67 (7) and 26.23 (7)° with the central ring. In the crystal, weak C-H⋯N and C-H⋯O inter-actions link the mol-ecules into a three-dimens...

The asymmetric unit of the title compound, C(18)H(12)N(4), consists of a half-mol-ecule, where the two halves of the mol-ecule are related by inversion symmetry. The mol-ecule is effectively planar, with the largest deviation from the 22-atom mean plane, measuring 0.024 (2) Å, exhibited by the ortho-C atom of the phenyl ring. The crystal structure...

In the title mol-ecule, C(13)H(16)O(4), the pyran ring is in a half-chair conformation. There is an intra-molecular hydrogen bond involving the ketone O atom and an H atom of a phenol group which forms an S(6) ring. The ketone O atom is also involved in an inter-molecular hydrogen bond with a different phenolic H atom of a symmetry-related mol-ecul...