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Abstract How emerging adulthood, a period particularly susceptible to the onset of mental disorders, responds to acute aerobic exercise effects on mood and brain remains an open question. A challenge in addressing this question is the scarcity of open data derived from scientific intervention paradigms. We recruited 83 healthy volunteers aged 17 to 24, who were randomly assigned to either an exercise group or a control group. The exercise group performed 30-minutes aerobic exercise with moderate intensity on a cycle ergometer, while the control group read neutral textual material without any physical activity. All participants received structural MRI scans before their intervention periods and completed mood scales and resting-state functional MRI scans before and after their intervention periods. Their heart rates were also monitored during the intervention. The dataset represents the first open resource for probing the acute aerobic exercise effects on brain and mind, containing physical, mental, and brain measurements. It has been released as part of the Chinese Color Nest Community in the Science Data Bank.

Abstract During the past decade, cognitive neuroscience has been calling for population diversity to address the challenge of validity and generalizability, ushering in a new era of population neuroscience. The developing Chinese Color Nest Project (devCCNP, 2013–2022), the first ten-year stage of the lifespan CCNP (2013–2032), is a two-stages project focusing on brain-mind development. The project aims to create and share a large-scale, longitudinal and multimodal dataset of typically developing children and adolescents (ages 6.0–17.9 at enrolment) in the Chinese population. The devCCNP houses not only phenotypes measured by demographic, biophysical, psychological and behavioural, cognitive, affective, and ocular-tracking assessments but also neurotypes measured with magnetic resonance imaging (MRI) of brain morphometry, resting-state function, naturalistic viewing function and diffusion structure. This Data Descriptor introduces the first data release of devCCNP including a total of 864 visits from 479 participants. Herein, we provided details of the experimental design, sampling strategies, and technical validation of the devCCNP resource. We demonstrate and discuss the potential of a multicohort longitudinal design to depict normative brain growth curves from the perspective of developmental population neuroscience. The devCCNP resource is shared as part of the “Chinese Data-sharing Warehouse for In-vivo Imaging Brain” in the Chinese Color Nest Project (CCNP) – Lifespan Brain-Mind Development Data Community ( https://ccnp.scidb.cn ) at the Science Data Bank.

Occult HBV infection (OBI) has been reported in infants born to HBsAg-positive mothers despite immunization. This study aims to determine the maintenance of this status in a prospective birth cohort.A total of 158 neonates born to HBsAg-positive mothers were enrolled. All received passive-active immunization against HBV according to a 0-1-6 schedule. Sera were collected at 7 months of age. Those diagnosed with OBI were serially followed up at 12, 24 and 36 months of age. HBV serological markers were determined by Abbott i2000 system. HBV DNA was quantitated by Abbott m2000 system. Standard PCR followed by direct sequencing were applied for mother-child HBV pairs. Homology and phylogenetic comparisons were done by BLAST and Mega 5.All the 158 neonates were HBsAg-negative and anti-HBs-positive at 7 months of age, and 32 (20.3%) of them were diagnosed with OBI, with a median HBV DNA level of 1.97 (1.20-3.71) log IU/mL. Of them, HBV DNA was positive in 25.0%, 21.9% and 7.7% at 12, 24 and 36 months of age, respectively. HBV DNA disappeared at one of the follow-up points in 31 neonates, however, rebounded to low levels in 6 of them thereafter. HBV DNA persisted at low levels during follow-ups in the other one neonate apart from the above 31. All remained negative for HBsAg. Only two (6.3%) neonates were positive for anti-HBc after 24 months of age. HBV showed close homology and phylogenetic relationships for mother-child pairs. S-escape mutant, G145R, was not discovered. The first vaccine dose within 6 hours of birth significantly reduced the occurrence of OBI (59.4% vs. 83.3%, p = 0.003).HBV may be controlled in immunized neonates of HBsAg-positive mothers, after being diagnosed with OBI. Timely vaccination against HBV may provide the utmost protection. Long-term and close monitorings are needed.

In the title compound, [Zn(C7H4ClO3)2(C12H8N2)(H2O)], the ZnII cation is coordinated by two 4-chloro-2-salicylate anions, one 1,10-phenanthroline ligand and one water molecule in a square-pyramidal coordination geometry; the Zn cation lies 0.4591 (11) Å from the basal plane. The benzene rings of the anions are involved in π–π stacking. The centroid–centroid distance between parallel benzene rings of adjacent molecules is 3.9017 (17) Å, and the centroid–centroid distance between benzene and pyridine rings of adjacent molecules is 3.584 (2) Å. Intramolecular O—H...O hydrogen bonding is present.

In the title compound, [ZnCl2(C9H7N)2], the ZnII cation is coordinated by two Cl− anions and two isoquinoline ligands in a distorted ZnCl2N2 tetrahedral geometry; the two isoquinoline ring systems are twisted with respect to each other at a dihedral angle of 45.72 (8)°. The parallel isoqiunoline ring systems of adjacent molecules are partially overlapped, with the shorter face-to-face distance of 3.438 (19) Å indicating the existence of weak π–π stacking in the crystal structure.

In the title centrosymmetric dimeric CdII complex, [Cd2(C7H5O4)4(C12H8N2)2(H2O)2], the CdII cation is coordinated by a bidentate phenanthroline (phen) ligand, three dihydroxybenzoate (dhba) anions and one water molecule in a distorted CdN2O4 octahedral geometry. Among the dhba anions, two anions bridge two CdII cations to form the dimeric complex with significant different Cd—O bond distances of 2.2215 (19) and 2.406 (2) Å. The centroid–centroid distance of 3.4615 (19) Å between two nearly parallel benzene rings of the dhba and phen ligands coordinating to the same CdII cation indicates the existence of intramolecular π–π stacking in the complex. Extensive O—H...O hydrogen bonding and intermolecular weak C—H...O hydrogen bonding help to stabilize the crystal structure. One hydroxy group of the monodentate dhba ligand is disordered over two sites with a site-occupancy ratio of 0.9:0.1.

In the title compound, [Co(C4H4O4)(C9H7N)2(H2O)2]n, the CoII cation, located on an inversion center, is coordinated by two succinate anions, two isoquinoline ligands and two water molecules in a distorted octahedral geometry. The succinate anion, located across another inversion center, bridges the Co cations, forming polymeric chains running along the b axis. The partially overlapped arrangement of parallel isoquinoline ring systems of adjacent polymeric chains and the shorter face-to-face distance of 3.402 (6) Å indicates the existence of weak π–π stacking in the crystal structure. Classical intra- and intermolecular O—H...O hydrogen bonding and weak non-classical intermolecular C—H...O hydrogen bonding help to stabilize the crystal structure.

The structure of the the title compound, [Cu2(C7H3ClO3)2(C12H8N2)2]·2H2O, consists of a dimeric unit involving a planar Cu2O2 group arranged around an inversion center. The coordination sphere of the CuII atom can be described as an elongated distorted square pyramid where the basal plane is formed by the two N atoms of the 1,10-phenanthroline molecule and the two O atoms of the hydroxychlorobenzoate (hcbe) anion. The long apical Cu—O distance of 2.569 (2) Å involves the O atom of a symmetry-related hcbe anion, building up the dinuclear unit. Each dinuclear unit is connected through O—H...O hydrogen bonds involving two water molecules, resulting in an R42(8) graph-set motif and building up an infinite chain parallel to (10overline{1}). C—H...O interactions further stabilize the chain.

In the crystal structure of the title compound, [Pb2(C4H5NO4)2(C6H6N4S2)2]·4H2O, the dinuclear PbII complex molecule is centrosymmetric. The Pb atom is chelated by a tridentate iminodiacetate anion (IDA) and a diaminobithiazole (DABT) ligand, while a carboxylate O atom from an adjacent IDA anion further bridges the Pb atom with a longer Pb—O bond [2.892 (3) Å]. The lone-pair electrons of the Pb atom occupy an axial site in the Ψ-pentagonal-bipyramidal coordination polyhedron. The IDA anion displays a facial configuration: its chelating five-membered rings assume an envelope configuration. Within the DABT ligand, the two thiazole rings are twisted relative to each other, making a dihedral angle of 9.51 (17)°. Extensive N—H...O, O—H...O and weak C—H...O hydrogen bonding helps to stabilize the crystal structure.

In the crystal structure of the title compound, {[MnNa(C6H4NO3)3]·H2O}n, the MnII cation is located on a threefold rotation axis and is chelated by three 2-oxidopyridinium-3-carboxylate (opc) anions in an octahedal coordination. The NaI cation is located on a threefold rotation axis and is surrounded by six O atoms from three opc anions. The opc anions link the Mn and Na cations, forming a three-dimensional polymeric structure. The uncoordinated water molecule, located on a threefold rotation axis, is equally disordered over two sites. The three-dimensional network is consolidated by N—H...O hydrogen bonds.

In the title centrosymmetric binuclear CuII complex, [Cu2(C8H7O2)4(C9H7N)2], the two Cu cations are bridged by four carboxylate groups of the phenylacetate anions; each Cu cation is further coordinated by an isoquinoline ligand to complete the distorted CuO4N square-pyramidal geometry. The Cu cation is displaced by 0.2092 (8) Å from the basal plane formed by the four O atoms. Within the dinuclear molecule, the Cu...Cu separation is 2.6453 (6) Å. Although a parallel, overlapped arrangement of isoquinoline ligands exists in the crystal structure; the longer face-to-face distance of 3.667 (5) Å suggests there is no π–π stacking between isoquinoline ring systems.

In the title complex, [Zn(C7H5O3)2(C10H8N2)(H2O)], the ZnII ion is coordinated by two 4-hydroxybenzoate anions, one 2,2′-bipyridine molecule and one water molecule and displays a distorted octahedral geometry. One Zn—O bond [2.5300 (15) Å] is much longer than the others in the molecule. In the crystal structure, the face-to-face separation of 3.547 (9) Å suggests no π–π stacking between parallel bipyridine ring systems, and an extensive O—H...O hydrogen-bonding network between the coordinated water molecule, the phenol group and carboxylate O atoms is present.

In the crystal structure of the title compound, [Cu2(CH3COO)4(C9H7N)2], the CuII cation is coordinated by four acetate anions and one isoquinoline molecule in a distorted square-pyramidal geometry; the CuII cation is 0.1681 (6) Å from the basal coordination plane formed by the four O atoms. Each acetate anion bridges two CuII cations to form the centrosymmetric dinuclear complex. Within the dinuclear molecule, the Cu...Cu separation is 2.6459 (4) Å. A parallel arrangement of isoquinoline ligands of adjacent complexes is observed in the crystal structure; the face-to-face distance of 3.610 (10) Å suggests there is no π–π stacking between isoquinoline ring systems.

In the molecule of the title CoII complex, [Co(C6H4NO3)2(C3H4N2)2], the CoII atom is located on a twofold rotation axis and chelated by two oxidopyridiniumcarboxylate anions and further cis-coordinated by two imidazole ligands in a distorted octahedral geometry. The shorter C—O bond distance of 1.260 (2) Å suggests electron delocalization between the oxido group and the pyridinium ring. The uncoordinated carboxylate O atom links with the imidazole and pyridinium rings of adjacent molecules via N—H...O hydrogen bonding. Weak C—H...O hydrogen bonding is also present in the crystal structure.

The title complex, [Zn(C7H4NO4)2(C5H5NO)2], has site symmetry 2. The ZnII ion is located on a crystallographic twofold rotation axis and assumes a distorted tetrahedral ZnN2O2 coordination geometry. Molecules are linked by an intermolecular O—H...O hydrogen bond and π–π stacking interactions between pyridine rings [centroid–centroid speparation 3.594 (1) Å].

In the crystal structure of the title NiII complex, [Ni(C6H4NO3)2(C3H4N2)2], the NiII atom is located on a twofold rotation axis and is chelated by two oxidopyridiniumcarboxylate anions and further cis-coordinated by two imidazole ligands in a distorted cis-N2O4 octahedral geometry. The C—O bond distance of 1.2573 (19) Å found for the non-coordinating O atom of the carboxylate group indicates significant delocalization of π-electron density over this residue. Similarly, the C—O bond distance of 1.260 (2) Å in the heteroaromatic ring indicates delocalization between the deprotonated hydroxy group and the pyridinium ring. The uncoordinated carboxylate O atom links with the imidazole and pyridinium rings of adjacent molecules via N—H...O and C—H...O hydrogen bonding, leading to a two-dimensional array parallel to (100).

The crystal structure of the title compound, (C10H9N2)2[Mn2(C10H8N2)3(H2O)8](C8H3O7S)2·C10H8N2·15H2O, consists of dinuclear MnII complex cations, sulfonatobenzenedicarboxylate trianions, 4-(4-pyridyl)pyridinium cations, uncoordinated 4,4′-bipyridine and uncoordinated water molecules. One 4,4′-bipyridine molecule bridges two Mn atoms, forming a centrosymmetric dinuclear complex; the mid-point of the C—C bond linking the pyridine rings of the bridging ligand is located on an inversion center. Each MnII atom is coordinated by four water and two 4,4′-bipyridine molecules in a distorted octahedral geometry. The MnII atom deviates by 0.591 (5) and 0.209 (2) Å from the mean planes of the coordinated pyridine rings. In the 4-(4-pyridyl)pyridinium cation, the two pyridine rings are twisted with respect to each other, making dihedral angle of 34.78 (17)°. The uncoordinated bipyridine molecule is also centrosymmetric. One of uncoordinated water molecules has site symmetry 2, and the other uncoordinated water molecule is located close to an inversion center and its one H atom is disordered equally over two sites. Extensive π–π stacking between pyridine rings is observed and an extensive hydrogen-bonding network of the types N—H...N, O—H...N and O—H...O is present.

In the crystal structure of the title polymeric complex, [Ca(C5H3N2O2)2]n, the CaII cation has site symmetry overline{4}m2 and is N,O-chelated by four pyrimidine-2-carboxylate anions in a square-antiprismatic geometry. The planar pyrimidine-2-carboxylate anion is located on a crystallographic special position, three C atoms have site symmetry 2mm, while the carboxyl O atom, the pyrimidine N atom and the other C atom have site symmetry m. Each pyrimidine-2-carboxylate anion bridges two CaII cations, forming polymeric sheets extending parallel to (001). π–π stacking exists between parallel pyrimidine rings [centroid–centroid distance = 3.6436 (6) Å] of adjacent polymeric sheets. Weak C—H...O hydrogen bonding is also observed between these sheets.

The crystal structure of the title compound, 2C5H6NO2+·C4H2O42−, consists of 3-hydroxypyridinium cations and fumarate dianions. The dianion is located on an inversion center and the cation is linked to it by O—H...O and N—H...O hydrogen bonds. The cation is twisted with respect to the anion by 24.83 (5)°.

The asymmetric unit of the title compound, [Co(C3H4N2)6][Co(C3H4N2)3(H2O)3](C12H6O4)2, contains two halves of crystallographically independent CoII complex cations, each assuming a distorted octahedral geometry, and one uncoordinated naphthalene-1,4-dicarboxylate dianion. One CoII cation is located on an inversion center and is coordinated by six imidazole molecules, while the other CoII cation is located on a twofold rotation axis and is coordinated by three water and three imidazole molecules. The uncoordinated naphthalene-1,4-dicarboxylate dianion links both CoII complex cations via O—H...O and N—H...O hydrogen bonding. One imidazole ligand is equally disordered over two sites about a twofold rotation axis, while the coordinated N atom of the imidazole is located on the twofold rotation axis. One water O atom has site symmetry 2.

In the crystal structure of the title cocrystal, 2C7H7NO·C4H4O4, the complete fumaric acid molecule is generated by a crystallographic inversion centre. The two components of the cocrystal are linked by an O—H...N hydrogen bond.

In the crystal structure of the title compound, [Na4Ni(C8H3O7S)2(H2O)12]n, the NiII cation occupies an inversion centre and is coordinated by the carboxyl groups of the sulfoisophthalate trianions and water molecules in a distorted octahedral geometry. Two independent NaI atoms are connected by the carboxyl and sulfonate groups of the sulfoisophthalate ligands anions and water molecules in a distorted octahedral geometry. The sulfoisophthalate ligands and coordinated water molecules bridge the NiII and NaI cations, forming a three-dimensional polymeric structure. Weak π–π stacking is present between parallel benzene rings [centroid–centroid distance = 3.9349 (10) Å]. Extensive O—H...O and C—H...O hydrogen bonding helps to stabilize the crystal structure.

The title compound, [CoNa4(C8H3O7S)2(H2O)12]n, is a three-dimensional coordination polymer bridged by sulfoisophthalate trianions and water molecules. The CoII atom, located on an inversion centre, is coordinated by two carboxylate groups of the sulfoisophthalate trianions and by four water molecules in a distorted CoO6 octahedral geometry. Two independent NaI atoms also have a distorted octahedral coordination geometry formed by water, carboxylate O and sulfonate O atoms. An extensive O—H...O and C—H...O hydrogen-bonding network is present in the crystal structure, as well as weak π-π stacking [centroid–centroid distance = 3.9553 (11) Å].

The crystal structure of the title compound, [Ni(C3H4N2)6][Ni(C3H4N2)3(H2O)3](C12H6O4)2, contains uncoordinated naphthalenedicarboxylate dianions and two kinds of NiII complex cations, both assuming distorted octahedral geometries. One NiII ion is located on an inversion center and is coordinated by six imidazole molecules, while the other NiII ion is located on a twofold rotation axis and is coordinated by three water molecules and three imidazole molecules in a mer-NiN3O3 arrangement. The naphthalenedicarboxylate dianion links both NiII complex cations via O—H...O and N—H...O hydrogen bonding, but no π–π stacking is observed between aromatic rings in the crystal structure. One imidazole ligand is equally disordered over two sites about a twofold rotation axis; one N atom and one water O atom have site symmetry 2.

In the title compound, [Co(C8H4O7S)(C12H8N2)(H2O)3]·H2O, the CoII cation is coordinated by one sulfoisophthalate dianion, one bidentate phenathroline (phen) molecule and three water molecules in a distorted cis-CoN2O4 octahedral geometry. In the crystal structure, aromatic π–π stacking occurs [centroid–centroid distances 3.7630 (14) and 3.7269 (15) Å], as well as an extensive O—H...O and C—H...O hydrogen-bonding network

The crystal structure of the title salt, [Mn(C10H8N2)(H2O)4][Mn2(C8H3O7S)2(C10H8N2)2(H2O)4]·4H2O, consists of mononuclear manganese(II) cations, dinuclear manganate(II) dianions and uncoordinated water molecules. The dianion is located about an inversion center; the MnII atom is coordinated by a 2,2′-bipyridine ligand, a sulfonatoisophthalate group, a water molecule along with two bridging water molecules in an octahedral geometry. The cation lies on a twofold rotation axis; the MnII atom is coordinated by four water molecules and a chelating 2,2′-bipyridine ligand in a distorted octahedral geometry. A partially overlapped arrangement between the bipyridine ligands and the aromatic ring of the sulfoisophthalate group of adjacent anions is observed; the distance (3.357 Å) indicates π–π stacking. Hydrogen bonds, with the water molecules serving as hydrogen-bond donors, lead to a three-dimensional network architecture.

In the crystal structure of the title compound, [Cd(C7H5O4)2(C12H8N2)2]·1.25H2O, the Cd2+ cation is coordinated by two phenanthroline (phen) molecules and two 2,5-dihydroxybenzoate (dhba) anions in a distorted octahedral geometry. The centroid–centroid distances of 3.809 (2) and 3.680 (2) Å between nearly parallel pyridine rings of the phen ligands and the benzene rings of dhba anions indicate that the dhba anions are involved in π–π stacking in the crystal structure. The face-to-face separation of 3.35 (3) Å between parallel phen ring systems also suggests π–π stacking between adjacent complex molecules. The crystal structure contains extensive O—H...O and C—H...O hydrogen bonding.

In the title compound, {[Cu(C12H6O4)(C3H4N2)2(H2O)]·2H2O}n, the CuII cation is coordinated by two naphthalene-1,4-dicarboxylate (naph) dianions, two imidazole molecules and one water molecule in a distorted square-pyramidal geometry. The Cu—O bond distance in the apical direction is 0.509 (3) Å longer than the mean Cu—O bond distance in the basal plane. The naph dianion bridges two CuII cations, forming a one-dimensional polymeric chain. The coordinated water molecule is hydrogen-bonded to the carboxylate groups and imidazole ligands of adjacent polymeric chains, forming a three-dimensional supramolecular structure. No À–À stacking is observed in the crystal structure. One solvent water molecule is disordered equally over two positions.

In the molecule of the title compound, [Ni(C5H4NO3S)2(H2O)4], the NiII cation is located on an inversion center and is coordinated by four water molecules and two pyridine-3-sulfonate anions with an NiN2O4 distorted octahedral geometry. The face-to-face separation of 3.561 (5) Å between parallel pyridine rings indicates the existence of weak π–π stacking between the pyridine rings. The structure also contains intermolecular O—H...O hydrogen bonding and weak C—H...O hydrogen bonding.

Eplerenone [systematic name: 7α-(methoxycarbonyl)-3-oxo-9α,11-epoxy-17α-pregn-4-ene-21,17-carbolactone], an aldosterone receptor antagonist, crystallizes from ethanol as a monosolvate, C24H30O6·C2H6O. The eplerenone molecule has two five-membered rings, three six-membered rings and one three-membered ring. Both five-membered rings display envelope conformations, while the three six-membered rings assume envelope (cyclohexene), half-chair (cyclohexane sharing one edge with epoxy) and chair (other cyclohexane) conformations. The solvent molecule is disordered equally over two sites. It is linked to the eplerenone molecule by hydrogen bonds.

In the crystal structure of the title compound, [Mn(C3H4N2)6][Mn(C3H4N2)3(H2O)3](C12H6O4)2, there are uncoordinated naphthalenedicarboxylate dianions and two kinds of MnII complex cations, both assuming a distorted octahedral geometry. One MnII cation is located on an inversion center and is coordinated by six imidazole molecules, while the other MnII cation is located on a twofold rotation axis and is coordinated by three water molecules and three imidazole units. The naphthalenedicarboxylate dianions are linked to both MnII complex cations via O—H...O and N—H...O hydrogen bonding, but no π–π stacking is observed between aromatic rings in the crystal structure.

The title compound, [Co4(C4H4O5)4(C7H6N2)8]·20H2O, consists of tetranuclear CoII complexes and disordered uncoordinated water molecules. The tetrameric complex molecule has overline{4} symmetry. While two benzimidazole molecules and a tridentate malate dianion coordinate a CoII ion, the carboxylate O atom from an adjacent malate dianion bridges the CoII ions to complete a distorted octahedral coordination geometry. The tridentate malate dianion chelates the CoII ion, and the chelate six- and five-membered rings show half-chair and envelope configurations, respectively. A face-to-face separation of 3.494 (9) Å between parallel benzimidazole ligands indicates the existence of π–π stacking between adjacent complexes. The crystal structure also involves N—H...O and O—H...O hydrogen bonds.

The title compound, [Ni2(C7H5O3)4(C7H6N2)4][Ni(C7H5O3)2(C7H6N2)2]·6H2O, is a mononuclear/dinuclear nickel(II) cocrystal, the two molecular species interacting through hydrogen bonds that involve the uncoordinated water molecules. In the mononuclear species, the NiII ion, located on an inversion center, is coordinated by two 1H-benzimidazole (bzim) ligands and two 3-hydroxybenzoate (hba) anions in a square-planar geometry. In the centrosymmetric dinuclear species, the NiII ion is coordinated by two bzim ligands and three hba anions in a square-pyramidal geometry; of the two independent hba anions, one bridges two NiII ions with both carboxylate and hydroxyl groups whereas the other coordinates in a unidentate manner to the NiII ion. The apical Ni—Ohydroxyl bond is 0.39 Å longer than the basal Ni—Ocarboxyl bonds. The face-to-face separation of 3.326 (9) Å indicates the existence of π–π stacking between parallel bzim ligands of adjacent dinuclear entities. Extensive N—H...O and O—H...O hydrogen bonds help to stabilize the crystal structure.

The crystal structure of the title compound, [Co(C7H5O3)(C12H8N2)2(H2O)](C7H5O3)·5H2O, consists of CoII complex cations, uncoordinated hydroxybenzoate anions and uncoordinated water molecules. The CoII ion is coordinated by two phenanthroline ligands, a water molecule and a 3-hydroxybenzoate anion, and displays a distorted octahedral geometry. π–π stacking is observed between parallel phenanthroline ligands, the face-to-face separations being 3.454 (19) and 3.435 (7) Å. An extensive hydrogen-bonding network helps to stabilize the crystal structure. The hydroxybenzoate ligand is disordered over two positions, with site occupancy factors 0.6 and 0.4. One solvent water molecule is also disordered over two positions, with site occupancy factors 0.6 and 0.4.

In the crystal strucuture of the title compound, C5H5N3O, which was obtained upon recrystallization of 2-cyanopyrimidine from aqueous sodium hydroxide, the amide group is twisted with respect to the aromatic ring by 24.9 (1)°. π–π stacking is observed between partially overlapped rings at a face-to-face separation of 3.439 (6) Å. The structure features a centrosymmetric pair of intermolecular N—H...O hydrogen bonds. Another N—H...O hydrogen bond between adjacent molecules links them into a helical chain motif.

The title compound, [Cu(C5H3N2O2)2], was prepared in a water–ethanol solution containing 2-cyanopyrimidine, malonic acid and copper(II) nitrate trihydrate. The CuII ion, located on an inversion center, is chelated by two pyrimidine-2-carboxylate anions in a CuO2N2 square-planar geometry. The uncoordinated carboxylate O atom and pyrimidine N atoms are linked to adjacent pyrimidine rings via weak C—H...O and C—H...N hydrogen bonding. π–π Stacking is observed between nearly parallel pyrimidine rings, the centroid-to-centroid separation being 3.8605 (13) Å.

In the title salt, [Co(C5H4N2O2)2(H2O)2]Cl2, the CoII ion is located on an inversion center. It is chelated by two neutral pyrimidine-2-carboxylic acid molecules and is coordinated by two water molecules in an octahedral coordination geometry. The cations and anions are linked via O—H...Cl hydrogen bonds into a layer structure; an intramolecular O—H...N hydrogen bond connects the carboxylic acid group to the pyrimidine N atom.