SYNTHESIS AND CHARACTERIZATION OF HYPERBRANCHED POLYURETHANE-BENZYLTETRAZOLE

A series of hyperbranched polyurethane-benzyltetrazoles(H-PBTZs) with different linkage structures were synthesized via the polycondensation of hexamethylenediisocyanate as an A_2 type monomer with(4-(1H-tetrazol-5- yl)benzyl)-diethanolamine(TBDEA) as a BB'_2 type monomer in the absence of catalyst at different temperatures.The FTIR, and ~(13)C and ~1H-NMR spectroscopy were used to characterize the molecular structures of TBDEA and H-PBTZs as well as the counterpart linear polyurethane-benzyltetrazole(L-...     

1,5-Di­amino-1H-1,2,3,4-tetrazole

In the title compound, CH₄N₆, the tetrazole ring is planar to within 0.001 (1) Å. The 5-amino group is conjugated with the π-system of the tetrazole ring. In contrast, the N atom of the 1-­amino group is sp³ hybridized and is not conjugated with the π system of the tetrazole ring. All H atoms are localized at the exocyclic N atoms. The mol­ecules are connected by N—H⃛N hydrogen bonds, forming an infinite three-dimensional framework.     

2,6-Di(1H-tetrazol-1-yl)pyridine and its cupric chloride complex

2,6-Di(1H-tetrazol-1-yl)pyridine (DTP) was prepared by a four-stage procedure, including step-by-step heterocyclization of both amino groups of 2,6-diaminopyridine with triethyl orthoformate and sodium azide. According to quantum-chemical calculations and single crystal X-ray diffraction data, DTP crystallizes in the form of the thermodynamically most stable conformer and has an almost flat molecular geometry. DTP was found to react with CuCl₂ ⋅ 2H₂O in ethanol to give the [Cu(DTP)Cl₂(H₂O)]_n complex, which is a 1D coordination polymer, formed at the expense of bridging DTP ligand via the tetrazole ring nitrogen atoms N⁴. Possible coordination cites in DTP molecule are discussed using the data of quantum chemical calculations. The pyridine ring nitrogen atom of DTP does not participate in the formation of either coordination or intermolecular hydrogen bonds. This is explained by the results of quantum chemical calculations showing that this atom is less basic than N3 and N4 atoms of DTP molecule.     

Zwitterionic 5‐(1‐piperidiniomethyl)‐1H‐tetrazolide

The title compound, C₇H₁₃N₅, a tetrazole analogue of betaines, exists as a zwitterion, with the H atom of the tetrazole ring being transferred to the piperidine ring N atom. The tetrazole ring symmetry is close to C_2v, which suggests strong charge delocalization in the N—C—N fragment of the ring. There are classical hydrogen bonds in the structure which are responsible for the formation of two‐membered aggregates.     

The layered structure of poly­[[di‐μ‐chloro‐bis­[chloro(2‐ethyl­tetrazole‐κN4)copper(II)]]‐di‐μ‐2‐ethyl­tetrazole‐κ2N1:N4]

In the polymeric title complex, [CuCl₂(C₃H₆N₄)₂]_n, there are two ligands in the asymmetric unit. The Cu atom adopts an elongated octahedral geometry, with two 2‐ethyl­tetrazole ligands [Cu—N = 2.0037 (16) and 2.0136 (16) Å] and two Cl atoms [Cu—Cl = 2.2595 (6) and 2.2796 (6) Å] in equatorial positions. A Cl atom and a symmetry‐related 2‐ethyl­tetrazole mol­ecule [Cu—Cl = 2.8845 (8) Å and Cu—N = 2.851 (2) Å] lie in the axial positions of the octahedron. One of the two 2‐­ethyltetrazole ligands of the asymmetric unit exhibits bidentate binding to two Cu atoms through two N atoms of the tetrazole ring, whereas the other ligand is coordinated in a monodentate fashion via one tetrazole N atom. The Cu‐atom octahedra form dimer entities by sharing edges with equatorial and axial Cl atoms. The dimers are linked together through the 2‐ethyl­tetrazole ligands to form one‐dimensional polymeric zigzag chains extending along the b axis. The chains are connected into infinite layers parallel to the (10) plane via the 2‐ethyl­tetrazole ligands.     

Supramolecular interactions in salts/cocrystals involving pyrimidine derivatives of sulfonate/carboxylic acid

The crystal structures of three compounds involving aminopyrimidine derivatives are reported, namely, 5-fluorocytosinium sulfanilate–5-fluorocytosine–4-azaniumylbenzene-1-sulfonate (1/1/1), C₄H₅FN₃O⁺·C₆H₆NO₃S⁻·C₄H₄FN₃O·C₆H₇NO₃S, I , 5-fluorocytosine–indole-3-propionic acid (1/1), C₄H₄FN₃O·C₁₁H₁₁NO₂, II , and 2,4,6-triaminopyrimidinium 3-nitrobenzoate, C₄H₈N₅⁺·C₇H₄NO₄⁻, III , which have been synthesized and characterized by single-crystal X-ray diffraction. In I , there are two 5-fluorocytosine (5FC) molecules (5FC-A and 5FC-B) in the asymmetric unit, with one of the protons disordered between them. 5FC-A and 5FC-B are linked by triple hydrogen bonds, generating two fused rings [two R₂²(8) ring motifs]. The 5FC-A molecules form a self-complementary base pair [R₂²(8) ring motif] via a pair of N—H…O hydrogen bonds and the 5FC-B molecules form a similar complementary base pair [R₂²(8) ring motif]. The combination of these two types of pairing generates a supramolecular ribbon. The 5FC molecules are further hydrogen bonded to the sulfanilate anions and sulfanilic acid molecules via N—H…O hydrogen bonds, generating R₄⁴(22) and R⁶₆(36) ring motifs. In cocrystal II , two types of base pairs (homosynthons) are observed via a pair of N—H…O/N—H…N hydrogen bonds, generating R₂²(8) ring motifs. The first type of base pair is formed by the interaction of an N—H group and the carbonyl O atom of 5FC molecules through a couple of N—H…O hydrogen bonds. Another type of base pair is formed via the amino group and a pyrimidine ring N atom of the 5FC molecules through a pair of N—H…N hydrogen bonds. The base pairs (via N—H…N hydrogen bonds) are further bridged by the carboxyl OH group of indole-3-propionic acid and the O atom of 5FC through O—H…O hydrogen bonds on either side of the R₂²(8) motif. This leads to a DDAA array. In salt III , one of the N atoms of the pyrimidine ring is protonated and interacts with the carboxylate group of the anion through N—H…O hydrogen bonds, leading to the primary ring motif R₂²(8). Furthermore, the 2,4,6-triaminopyrimidinium (TAP) cations form base pairs [R₂²(8) homosynthon] via N—H…N hydrogen bonds. A carboxylate O atom of the 3-nitrobenzoate anion bridges two of the amino groups on either side of the paired TAP cations to form another ring [R₃²(8)]. This leads to the generation of a quadruple DADA array. The crystal structures are further stabilized by π–π stacking ( I and III ), C—H…π ( I and II ), C—F…π ( I ) and C—O…π ( II ) interactions.     

Mass spectometry of aralkyl compounds with a functional group—VI1: Mass spectra of 1-phenylethyanol-1, 2-phenylethanol-1 and 1-phenylpropanol-2

Mass spectra of 1-phenylethanol-1 and its analogues, specifically deuterated in the aliphatic chain, suggest that the [M? CH₃]⁺ ion is represented partly by an α-hydroxybenzyl fragment. Moreover, the molecular ion loses successively—after scrambling of all hydrogen atoms, except those of CH₃? a hydrogen atom and C₆H₆, generation the CH₃CO⁺ ion. Diffuse peaks, found in the spectra of of 2-phenylethanol-1 and its analogues, specifically deuterated in the aliphatic chain and in the phenyl ring, show that the molecular ion loses C₂H₄O, possibly via a four-center mechanism, after an exchange of aromatic and hydroxylic hydrogens. Mass spectra of 1-phenylpropanol-2 and its analogues, specifically, deuterated in the aliphatic chain, demonstrate that in the molecular ion exclusively the hydroxyl hydrogen atom is transferred to one of the ortho-positions of the phenyl ring via a McLafferty rearrangement, generating the [M ? C₂H₄O]⁺ ion. Furtherore, an eight-membered ring structure is proposed for the [M ? CH₃]⁺ ion to explain the loss of H₂O and C₂H₂O from this ion after an extensive scrambling of hydrogen atoms.     

REVERSE ATOM TRANSFER RADICAL POLYMERIZATION OF STYRENE WITH COPPER-BASED CATALYST

 "Living"/controlled radical polymerization of styrene was carried out with diethyl 2,3-dicyano-2,3-diphenylsuccinate (DCDPS)/CuCl₂/bipyridine (bipy) initiation system at 120℃. The molecular weights of resultant PSt increased with the monomer conversion and the polydispersities were in the range of 1.37 ～ 1.52. A linear ln([M]o/[M])versus time plot was also obtained indicating the constant concentration of growing radicals during the polymerization with this initiation system. End group analysis by ¹H-NMR spectroscopic studies showed that the end groups of the polymer obtained is cω-functionalized by a chlorine group from the catalyst and a-functionalized by a (carbethoxy-cyano-phenyl)methyl group from the fragments of the initiator. Having C1 atom at the chain end, the PSt obtained can be used as a macroinitiator to promote a chain-extension reaction with fresh St and block copolymerization reaction with a second monomer, such as methyl methacrylate, in the presence of CuC1/bipy catalyst via a conventional ATRP process.     

Quantitative <Superscript>2</Superscript>H NMR spectroscopy

The selectivity of deuterium distribution between the nonequivalent positions in 3-carene (1), 4-α-acetyl-2-carene (2), and 4-(1-hydroxyethyl)-2-carene (3) has been measured by ²H-{¹H} NMR spectroscopy at the natural abundance of deuterium. These “H/D-isotope portraits” were shown to be typical of terpenes and terpenoids produced in plants via the biosynthetic DXP pathway. The mechanism of acylation of 1 was studied by the density functional theory method (PBE functional, TZ2p basis set). The six-membered ring in compound 1 is planar. However, the endo attack of electrophiles on this ring is more favorable both kinetically and thermodynamically. It was shown both experimentally and theoretically that the elimination of a hydrogen atom in the second reaction step proceeds stereoselectively at the C(2) atom from the anti position with respect to the three-membered ring and occurs with pronounced nucleophilic assistance from the carbonyl group. For Part 2, see Ref. 1. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1657–1664, August, 2008.     

Supramolecular architectures in cytosinium 6‐chloronicotinate monohydrate and 5‐bromo‐6‐methylisocytosinium hydrogen sulfate

Aminopyrimidine derivatives are biologically important as they are components of nucleic acids and drugs. The crystals of two new salts, namely cytosinium 6‐chloronicotinate monohydrate, C₄H₆N₃O⁺·C₆H₃ClNO₂⁻·H₂O, ( I ), and 5‐bromo‐6‐methylisocytosinium hydrogen sulfate (or 2‐amino‐5‐bromo‐4‐oxo‐6‐methylpyrimidinium hydrogen sulfate), C₅H₇BrN₃O⁺·HSO₄⁻, ( II ), have been prepared and characterized by single‐crystal X‐ray diffraction. The pyrimidine ring of both compounds is protonated at the imine N atom. In hydrated salt ( I ), the primary R₂²(8) ring motif (supramolecular heterosynthon) is formed via a pair of N—H…O(carboxylate) hydrogen bonds. The cations, anions and water molecule are hydrogen bonded through N—H…O, N—H…N, O—H…O and C—H…O hydrogen bonds, forming R₂²(8), R₃²(7) and R₅⁵(21) motifs, leading to a hydrogen‐bonded supramolecular sheet structure. The supramolecular double sheet structure is formed via water–carboxylate O—H…O hydrogen bonds and π–π interactions between the anions and the cations. In salt ( II ), the hydrogen sulfate ions are linked via O—H…O hydrogen bonds to generate zigzag chains. The aminopyrimidinium cations are embedded between these zigzag chains. Each hydrogen sulfate ion bridges two cations via pairs of N—H…O hydrogen bonds and vice versa, generating two R₂²(8) ring motifs (supramolecular heterosynthon). The cations also interact with one another via halogen–halogen (Br…Br) and halogen–oxygen (Br…O) interactions.     

Hexa‐μ2‐chloro‐μ4‐oxo‐tetrakis[(2‐ethyl­tetrazole‐κN4)copper(II)]

In the title molecular complex, [Cu₄Cl₆O(2‐EtTz)₄], where 2‐EtTz is 2‐ethyl­tetrazole (C₃H₆N₄), the central O atom is located on the symmetry site and is tetrahedrally coordinated to four Cu atoms, with Cu—O distances of 1.8966 (4) Å. A very slight distortion of Cu₄O from a regular tetrahedron is observed [two Cu—O—Cu angles are 108.76 (3)° and four others are 109.828 (13)°]. Each Cu atom is connected to three others via the Cl atoms, forming a slightly distorted Cl octahedron around the O atom, with O⋯Cl distances of 2.9265 (7) Å for Cl atoms lying on the twofold axis and 2.9441 (13) Å for those in general positions. The Cu atom has a distorted trigonal–bipyramidal environment, with three Cl atoms in the equatorial plane, and with the N atom of the 2‐ethyl­tetrazole ligand and the μ₄‐O atom in axial positions. The Cu atom is displaced out of the equatorial plane by ca 0.91 Å towards the coordinated N atom of the 2‐­ethyl­tetrazole ligand.     

A tetrazol‐5‐yl analogue of glycine, 5‐ammoniomethyl‐1H‐tetrazolide,and its copper(II) complex

A nonclassical tetrazole isostere of glycine, viz. zwitterionic 5‐ammoniomethyl‐1H‐tetrazolide, C₂H₅N₅, (I), crystallizes in the chiral P3₁ space group, similar to γ‐glycine. The crystal packing of (I) is determined by a set of classical hydrogen bonds, forming a three‐dimensional network that is practically the same as that in γ‐glycine. The Cu^II complex of (I), poly[[bis(μ₂‐5‐aminomethyl‐1H‐tetrazolido‐κ³N¹,N⁵:N⁴)copper(II)] dihydrate], {[Cu(C₂H₄N₅)₂]·2H₂O}_n, (II), is a layered coordination polymer formed as a result of tetrazole ring bridges. The Cu^II cations lie on inversion centres, are surrounded by four anions and adopt elongated octahedral coordination. Water molecules are located in the interlayer space and connect the layers into a three‐dimensional network via a system of hydrogen bonds.     

Multiple intramolecular hydrogen bonds in 2,4‐di‐tert‐butyl‐6‐[N‐(2,6‐diisopropylphenyl)‐P,P‐diphenylphosphorimidoyl]phenol

The title compound, C₃₈H₄₈NOP, isolated from the reaction of (2‐diphenylphosphanyl‐4,6‐di‐tert‐butyl)phenol with 2,6‐diisopropylphenyl azide at 273 K, can act as an N,O‐bidentate ligand. Crystal structure analysis shows a deviation from ideal tetrahedral symmetry around the P atom. The molecule exists as a monomer in the solid state, whose conformation is stabilized via multiple intramolecular hydrogen bonds. Geometric parameters from both experimental and theoretical calculations are compared.     

A one‐dimensional silver(I) coordination polymer based on an asymmetric flexible N‐donor carboxylate ligand: catena‐poly[(μ3‐4‐{[(1‐phenyl‐1H‐tetrazol‐5‐yl)sulfanyl]methyl}benzoato‐κ3O:O′:N4)silver(I)]

The title compound, [Ag(C₁₅H₁₁N₄O₂S)]_n, was synthesized by the reaction of 4‐{[(1‐phenyl‐1H‐tetrazol‐5‐yl)sulfanyl]methyl}benzoic acid (Hptmba) with silver nitrate and triethylamine at room temperature. The asymmetric unit contains one crystallographically independent Ag^I cation and one ptmba⁻ ligand. Each Ag^I cation is tricoordinated by two carboxylate O atoms and one tetrazole N atom from three different ptmba⁻ ligands, displaying a distorted T‐shaped geometry. Three Ag^I cations are linked by tris‐monodentate bridging ptmba⁻ ligands to form a one‐dimensional double chain along the c axis, which is further consolidated by an intrachain π–π contact with an offset face‐to‐face distance of 4.176 (3) Å between the centroids of two adjacent aromatic rings in neighbouring benzoate groups. The one‐dimensional chains are linked into a three‐dimensional supramolecular framework by additional π–π interchain interactions, viz. of 3.753 (3) Å between two phenyl substituents of the tetrazole rings and of 4.326 (2) Å between a benzoate ring and a tetrazole ring. Thermogravimetric analysis and the fluorescence spectrum of the title compound reveal its good thermal stability and a strong green luminescence at room temperature.     

Green chemistry synthesis: 2‐amino‐3‐[(E)‐(2‐pyridyl)methylideneamino]but‐2‐enedinitrile monohydrate and 5‐cyano‐2‐(2‐pyridyl)‐1‐(2‐pyridylmethyl)‐1H‐imidazole‐4‐carboxamide

The title compounds, C₁₀H₉N₅O·H₂O (L1·H₂O) and C₁₆H₁₂N₆O (L2), were synthesized by solvent‐free aldol condensation at room temperature. L1, prepared by grinding picolinaldehyde with 2,3‐diamino‐3‐isocyanoacrylonitrile in a 1:1 molar ratio, crystallized as a monohydrate. L2 was prepared by grinding picolinaldehyde with 2,3‐diamino‐3‐isocyanoacrylonitrile in a 2:1 molar ratio. By varying the conditions of crystallization it was possible to obtain two polymorphs, viz. L2‐I and L2‐II; both crystallized in the monoclinic space group P2₁/c. They differ in the orientation of one pyridine ring with respect to the plane of the imidazole ring. In L2‐I, this ring is oriented towards and above the imidazole ring, while in L2‐II it is rotated away from and below the imidazole ring. In all three molecules, there is a short intramolecular N—H...N contact inherent to the planarity of the systems. In L1·H₂O, this involves an amino H atom and the C=N N atom, while in L2 it involves an amino H atom and an imidazole N atom. In the crystal structure of L1·H₂O, there are N—H...O and O—H...O intermolecular hydrogen bonds which link the molecules to form two‐dimensional networks which stack along [001]. These networks are further linked via intermolecular N—H...N(cyano) hydrogen bonds to form an extended three‐dimensional network. In the crystal structure of L2‐I, symmetry‐related molecules are linked via N—H...N hydrogen bonds, leading to the formation of dimers centred about inversion centres. These dimers are further linked via N—H...O hydrogen bonds involving the amide group, also centred about inversion centres, to form a one‐dimensional arrangement propagating in [100]. In the crystal structure of L2‐II, the presence of intermolecular N—H...O hydrogen bonds involving the amide group results in the formation of dimers centred about inversion centres. These are linked via N—H...N hydrogen bonds involving the second amide H atom and the cyano N atom, to form two‐dimensional networks in the bc plane. In L2‐I and L2‐II, C—H...π and π–π interactions are also present.     

The first square‐planar copper(II) 1:2 complex with differently coordinated 2‐hydroxybenzaldehyde 4‐allylthiosemicarbazone ligands

The title compound, [(Z)‐4‐allyl‐2‐(2‐hydroxybenzylidene)thiosemicarbazide‐κS][(E)‐4‐allyl‐1‐(2‐oxidobenzylidene)thiosemicarbazidato‐κ³O,N¹,S]copper(II) monohydrate, [Cu(C₁₁H₁₁N₃OS)(C₁₁H₁₃N₃OS)]·H₂O, crystallized as a rotational twin in the monoclinic crystal system (space group Cc) with two formula unit (Z′ = 2) in the asymmetric unit, one of which contains an allyl substituent disordered over two positions. The Cu^II atom exhibits a distorted square‐planar geometry involving two differently coordinated thiosemicarbazone ligands. One ligand is bonded to the Cu^II atom in a tridentate manner via the phenolate O, azomethine N and thioamide S atoms, while the other coordinates in a monodentate manner via the S atom only. The complex is stabilized by an intramolecular hydrogen bond, which creates a six‐membered pseudo‐chelate metalla‐ring. The structure analysis indicates the presence of the E isomer for the tridentate ligand and the Z isomer for the monodentate ligand. The crystal structure contains a three‐dimensional network built from intermolecular O—H...O, N—H...O, O—H...N and N—H...S hydrogen bonds.     

Atom Transfer Radical Polymerization of Butadiene Initiated by Benzyl Chloride/MoCl5 Substituted by 1-octanol/PPh3

A novel initiator system, benzyl chloride/MoCl₅ substituted by 1-octanol/triphenyl phosphine (PPh₃), was applied to the atom transfer radical polymerization (ATRP) of butadiene. The characterization revealed the linear increase of the number average molecular weight with the monomer conversion and the rather wide molecular weight distributions of the polymerization products. The microstructure of the butadiene was detected by IR and ¹H-NMR. The chlorine atom at ω –end group of the polymer and the change of valence states of molybdenum detected by UV–Vis spectra revealed that the polymerization accorded primarily with the mechanism of ATRP.     

The mutual influence of the imine substituents of terephthal-bis-imines concerning their reactivity towards Fe2(CO)9

The reaction of terephthal-bis-imines with Fe₂(CO)₉ proceeds via a C---H activation reaction in the ortho position with respect to one of the imine functions. The corresponding hydrogen atom is shifted towards the former imine carbon atom producing a methylene group instead. The dinuclear iron complexes formed by this reaction sequence and showing no coordination of the second imine group were isolated from reactions of bis-imines with both phenyl and cyclohexyl substituents at the imine nitrogen atoms. In addition, we observed three different reaction pathways of the second imine substituent of the starting material which is obviously thus influenced by the fact that the first one is coordinating an Fe₂(CO)₆ moiety. If the organic substituent at the imine nitrogen atoms is a phenyl group the formation of a trinuclear complex is achieved in which an additional Fe(CO)₃ group is coordinating the CN double bond and one of the carbon---carbon bonds of the central phenyl ring in an η⁴-fashion. The same reaction leads to the isolation of a tetranuclear iron---carbonyl compound in which both imine substituents were transformed via the pathway described above, each building up dinuclear subunits. In contrast to this the reaction of a bis-imine with cyclohexyl groups at the imine nitrogen and thus an enhanced nucleophilicity leads to the formation of a tetranuclear complex in which only one imine group reacts under C---H activation with subsequent hydrogen migration towards the former imine carbon atom. The second imine substituent also shows a C---H activation reaction in the ortho position with respect to the imine group but the corresponding hydrogen atom is transferred to one of the aromatic carbon atom of the central phenyl ring of the ligand. The C=N double bond remains unreacted and only coordinates the second Fe₂(CO)₆ moiety via the nitrogen lone pair.     

Supramolecular Ribbons. Crystal Structure and Spectroscopic Properties of 2,2′-Bipyrroyl

Summary.  A crystal structure determination of 2,2′-bipyrroyl (1; 2,2′-dipyrryl-diketone, bis (2-pyrrolyl)ethanedione) and its spectroscopic properties in solution are reported. In the crystal, 1 self-assembles via hydrogen bonding into supramolecular ribbons that extend indefinitely through the crystal lattice. The observed molecular conformation is one where each pyrrole ring and adjacent carbonyl group are co-planar (torsion angle ∼ 0.9°), with the N-H pointing in the same direction as the C=O. The two carbonyls have a transoid but not co-planar geometry with a torsion angle of ∼128°. Adjacent molecules in the crystal are linked by pairs of intermolecular hydrogen bonds, pyrrole NH to carbonyl oxygen, to form a matrix of polymeric chains that lie like neatly stacked, parallel streams of ribbons. Molecular mechanics calculations on the monomer indicate an intra-molecularly hydrogen bonded planar conformation (sp, ap, sp) at the global energy minimum. In CHCl₃, 1 is monomeric according to vapor pressure osmometry (MW _obs=179±10 vsċMW _calc=188). In THF, the measured molecular weight is 340±15, which corresponds best to one molecule of 1 solvated by two THF molecules (MW=322 for C₁₀H₈N₂O₄ċ2 C₄H₈O) rather than to a dimer. Received October 21, 1999. Accepted November 2, 1999     

trans‐Bis(dimethyl sulfoxide‐κO)bis(3‐oxo‐3,4‐dihydroquinoxaline‐2‐carboxylato‐κ2N1,O2)copper(II)

The title compound, [Cu(C₉H₅N₂O₃)₂(C₂H₆OS)₂], consists of octahedrally coordinated Cu^II ions, with the 3‐oxo‐3,4‐dihydroquinoxaline‐2‐carboxylate ligands acting in a bidentate manner [Cu—O = 1.9116 (14) Å and Cu—N = 2.1191 (16) Å] and a dimethyl sulfoxide (DMSO) molecule coordinated axially via the O atom [Cu—O = 2.336 (5) and 2.418 (7) Å for the major and minor disorder components, respectively]. The whole DMSO molecule exhibits positional disorder [0.62 (1):0.38 (1)]. The octahedron around the Cu^II atom, which lies on an inversion centre, is elongated in the axial direction, exhibiting a Jahn–Teller effect. The ligand exhibits tautomerization by H‐atom transfer from the hydroxyl group at position 3 to the N atom at position 4 of the quinoxaline ring of the ligand. The complex molecules are linked through an intermolecular N—H...O hydrogen bond [N...O = 2.838 (2) Å] formed between the quinoxaline NH group and a carboxylate O atom, and by a weak intermolecular C—H...O hydrogen bond [3.392 (11) Å] formed between a carboxylate O atom and a methyl C atom of the DMSO ligand. There is a weak intramolecular C—H...O hydrogen bond [3.065 (3) Å] formed between a benzene CH group and a carboxylate O atom.