Pyrazine Nitrogen Atoms Research Articles

Potency and Target Surface Interaction of Diazinoyl Nicotinic Insecticides.

Structure-activity relationships of diazinoyl nicotinic insecticides (diazinoyl isomers and 5- or 6-substituted pyrazin-2-oyl analogues) are considered in terms of affinity to the insect nicotinic acetylcholine receptor (nAChR) and insecticidal activity against the imidacloprid-resistant brown planthopper. Among the test compounds, 3-(6-chloropyridin-3-ylmethyl)-2-(pyrazinoyl)iminothiazoline shows the highest potency in nAChR affinity and insecticidal activity. Aplysia californica acetylcholine binding protein (AChBP) mutants (Y55W + Q57R and Y55W + Q57T) are utilized to compare molecular recognition of nicotinic insecticides with diverse pharmacophores. N-nitro- or N-cyanoimine imidacloprid or acetamiprid, respectively, exhibits a high affinity to these AChBP mutants at a similar potency level. Intriguingly, the pyrazin-2-oyl analogue has a higher affinity to AChBP Y55W + Q57R than that to Y55W + Q57T, thereby indicating that pyrazine nitrogen atoms contact Arg57 guanidinium and Trp55 indole NH. Furthermore, nicotine prefers AChBP Y55W + Q57T over Y55W + Q57R, conceivably suggesting that the protonated nicotine is repulsed by Arg57 guanidinium, consistent with its inferior potency to insect nAChR.

Water-soluble dye – ZnII octacarboxy substituted tetrapyrazinoporphyrazine: Spectral-luminescence study of behavior in aqueous solutions

ZnII complex of octacarboxy substituted tetrapyrazinoporohyrazine, ZnTPyzPA(COOH)8, was prepared by mild alkaline hydrolysis of the corresponding octaethyl ester, ZnTPyzPA(COOEt)8, which was synthesized by template cycloteramerization of 5,6-di(ethoxycarbonyl)pyrazine-2,3-dicarbonitrile in the presence zinc(II) acetate in o-dichlorobenzene. Both complexes were characterized by IR, UV–vis, NMR spectroscopy (1H, 13C). Conformational analysis performed by DFT method in agreement with spectral study indicates that one of COOH group in each pyrazine ring participates in intramolecular hydrogen bonding with the adjacent pyrazine nitrogen atom. Unlike octacarboxy substituted ZnII phthalocyanine, ZnTPyzPA(COOH)8 remains non-aggregated not only in the octaanionic form present in the basic medium but also in tetraanioinic form existing in acid aqueous solutions since intramolecular H-bonding prevents intermolecular interactions. However, the fluorescence is almost completely quenched for tetraanion which can be related to the proton transfer in the excited state from carboxylic group to the pyrazine nitrogen. Aggregation is observed only for non-ionized form of ZnTPyzPA(COOH)8 existing in strongly acidic medium (1 M HCl solution, pH < 1).

Building a high-performance organic cathode material containing electron-withdrawing groups for lithium-ion batteries

The capacity of cathode materials is one of the main factors to limit the performance of lithium-ion batteries (LIBs), so it is urgent to develop high-performance cathode materials. Herein, trinitrohexaazatrinaphythylene (TNHATN) including an electron-withdrawing group (nitro, -NO2) was synthesized by the condensation reaction between hexaketocyclohexane and 4-nitro-o-phenylenediamine, and it was first investigated as a cathode material for lithium-ion batteries. The TNHATN electrode displays a high discharge specific capacity of 355.7 mAh g−1 at 0.05 A g−1 and a superior cycling stability, having the capacity retention of 97.9 % after 200 cycles. The excellent behaviors may be ascribed to its π-conjugated structure including electron-withdrawing groups and multiple redox active sites. The experimental results reveal the redox active sites are pyrazine nitrogen atoms and oxygen atoms from nitro groups. This work confirms that it is an effective route to introduce an electron-withdrawing group into a π-conjugated compound for obtaining high-performance organic cathode materials of LIBs.

Copper(ii) and silver(i) complexes with dimethyl 6-(pyrazine-2-yl)pyridine-3,4-dicarboxylate (py-2pz): the influence of the metal ion on the antimicrobial potential of the complex.

Dimethyl 6-(pyrazine-2-yl)pyridine-3,4-dicarboxylate (py-2pz) was used as a ligand for the synthesis of new copper(ii) and silver(i) complexes, [CuCl2(py-2pz)]2 (1), [Cu(CF3SO3)(H2O)(py-2pz)2]CF3SO3·2H2O (2), [Ag(py-2pz)2]PF6 (3) and {[Ag(NO3)(py-2pz)]·0.5H2O} n (4). The complexes were characterized by spectroscopic and electrochemical methods, while their structures were determined by single crystal X-ray diffraction analysis. The X-ray analysis revealed the bidentate coordination mode of py-2pz to the corresponding metal ion via its pyridine and pyrazine nitrogen atoms in all complexes, while in polynuclear complex 4, the heterocyclic pyrazine ring of one py-2pz additionally behaves as a bridging ligand between two Ag(i) ions. DFT calculations were performed to elucidate the structures of the investigated complexes in solution. The antimicrobial potential of the complexes 1-4 was evaluated against two bacterial (Pseudomonas aeruginosa and Staphylococcus aureus) and two Candida (C. albicans and C. parapsilosis) species. Silver(i) complexes 3 and 4 have shown good antibacterial and antifungal properties with minimal inhibitory concentration (MIC) values ranging from 4.9 to 39.0 μM (3.9-31.2 μg mL-1). All complexes inhibited the filamentation of C. albicans and hyphae formation, while silver(i) complexes 3 and 4 had also the ability to inhibit the biofilm formation process of this fungus. The binding affinity of the complexes 1-4 with calf thymus DNA (ct-DNA) and bovine serum albumin (BSA) was studied by fluorescence emission spectroscopy to clarify the mode of their antimicrobial activity. Catechol oxidase biomimetic catalytic activity of copper(ii) complexes 1 and 2 was additionally investigated by using 3,5-di-tert-butylcatechol (3,5-DTBC) and o-aminophenol (OAP) as substrates.

Pyrazine-bridged cobalt porphyrin: Characterization, unique crystal structure and computational studies

The synthesis, crystal structures and theoretical studies of two cobalt porphyrins, [CoII(TDMPP)] (1a) and [{CoII(TDMPP)}2(pyz)] (1b), (TDMPP = meso‑5,10,15,20-tetrakis(3,5-dimethoxyphenyl)porphyrin, pyz= pyrazine) is discussed. In 1b, the pyrazine is bridged between two Co-porphyrin moieties forming a binuclear Co(II) porphyrin complex. The Co•••Co nonbonding distance between two cobalt metal is 7.11 Å. This is the first report where two cobalt porphyrins are joined via a bridging pyrazine ligand. The bonding interactions of two bridged Co(II) porphyrins via the ligand is discussed using energy of frontier molecular orbitals and natural bond orbital analysis. Natural bond orbital (NBO) analysis shows that the charge transfer from the lone pair of pyrazine nitrogen atom to the anti-bonding orbital of metal cobalt (lpN(pyz)→lpCo*) has a significant role in the stabilization of the pyrazine bound structure.

Capturing Visible Light in Low-Band-Gap C4 N-Derived Responsive Bifunctional Air Electrodes for Solar Energy Conversion and Storage.

We report facile synthesis of low-band-gap mesoporous C4 N particles and their use as responsive bifunctional oxygen catalysts for visible-light-sensitive (VLS) rechargeable Zn-air battery (RZAB) and polymer-air battery (RPAB). Compared to widely studied g-C3 N4 , C4 N shows a smaller band gap of 1.99 eV, with a larger photocurrent response, and it can function as visible-light-harvesting antenna and bifunctional oxygen reduction/evolution (ORR/OER) catalysts, enabling effective photocoupling to tune oxygen catalysis. The C4 N-enabled VLS-RZAB displays a low charge voltage of 1.35 V under visible light, which is below the theoretical RZAB voltage of 1.65 V, corresponding to a high energy efficiency of 97.78 %. Pairing a C4 N cathode with a polymer anode also endows an VLS-RPAB with light-boosted charge performance. It is revealed that the ORR and OER active sites in C4 N are separate carbon sites near pyrazine-nitrogen atoms and photogenerated energetic holes can activate OER for improved reaction kinetics.

Practical and Computational Studies of Bivalence Metal Complexes of Sulfaclozine and Biological Studies.

In the search for novel, metal-based drug complexes that may be of value as anticancer agents, five new transition metal complexes of sulfaclozine (SCZ) with Cu(II), Co(II), Ni(II), Zn(II), and Fe(II) were successfully synthesized. The chemical structure of each complex was characterized using elemental analysis (CHN), IR spectroscopy, UV–Vis spectroscopy, thermogravimetric analysis (TGA), and electronic paramagnetic resonance (EPR) spectroscopy. IR spectra indicated that the donor atoms were one sulfonyl oxygen atom and one pyrazine nitrogen atom, which associated with the metal ions to form a stable hexagonal coordination ring. The metal–ligand stability constant (Kf) revealed that Cu(II) and Ni(II) have good coordination stability among the metal compounds. Theoretical studies using DFT/B3LYP were performed to further validate the proposed structures. The obtained results indicated that Cu(II) has a trigonal bipyramidal geometry, whereas Fe(II), Co(II), and Ni(II) have an octahedral structure, while Zn(II) has a tetrahedral arrangement. The bio-activities of the characterized complexes were evaluated using DNA binding titration and molecular docking. The binding constant values for the metal complexes were promising, with a maximum value for the copper metal ion complex, which was 9 × 105 M-1. Molecular docking simulations were also carried out to evaluate the interaction strength and properties of the synthesized metal complexes with both DNA and selected cancer-relevant proteins. These results were supported by in vitro cytotoxicity assays showing that the Cu(II) and Ni(II) complexes display promising antitumor activity against colon and breast cancer cell lines.

Hydrogen bond synthons affect the coordination geometry of d10-metal halide complexes: synthetic methods, theoretical studies, and supramolecular architectures

The tendency of the pyrazine nitrogen atom to form hydrogen bond supramolecular synthons affects the coordination geometry of new d10-metal halide complexes which have been prepared by solution-based methods in comparison with solid-state reactions.

Molecular Interactions of Pyrazine-Based Compounds to Proteins.

Pyrazine-based compounds are of great importance in medicinal chemistry. Due to their heteroaromatic nature, they uniquely combine properties of heteroatoms (polar interactions) with the properties of aromatic moieties (nonpolar interactions). This review summarizes results of a systematic analysis of RCSB PDB database focused on important binding interactions of pyrazine-based ligands cocrystallized in protein targets. The most frequent interaction of pyrazine was hydrogen bond to pyrazine nitrogen atom as an acceptor, followed by weak hydrogen bond with pyrazine hydrogen as donor. We also identified intramolecular hydrogen bonds within pyrazine ligands, π-interactions, coordination to metal ions, and few halogen bonds in chloropyrazines. In many cases the binding mode of the pyrazine fragment was complex, involving a combination of several interactions. We conclude that pyrazine as a molecular fragment should not be perceived as a simple aromatic isostere but rather as a readily interacting moiety of drug-like molecules with high potential for interactions to proteins.

Dynamic Covalent Synthesis of Crystalline Porous Graphitic Frameworks

Summary Porous graphitic framework (PGF) is a two-dimensional (2D) material that has emerging energy applications. An archetype contains stacked 2D layers, the structure of which features a fully annulated aromatic skeleton with embedded heteroatoms and periodic pores. Due to the lack of a rational approach in establishing in-plane order under mild synthetic conditions, the structural integrity of PGF has remained elusive and ultimately limited its material performance. Here, we report the discovery of the unusual dynamic character of the C=N bonds in the aromatic pyrazine ring system under basic aqueous conditions, which enables the successful synthesis of a crystalline porous nitrogenous graphitic framework with remarkable in-plane order, as evidenced by powder X-ray diffraction studies and direct visualization using high-resolution transmission electron microscopy. The crystalline framework displays superior performance as a cathode material for lithium-ion batteries, outperforming the amorphous counterparts in terms of capacity and cycle stability.

Salt of Ring‐Reduced Iron(II) Octaethyltetrapyrazinoporphyrazine Containing Trimetallic Dianions with Peripherally Coordinated ZnCl2 Units: {FeII(TPyzPzEt8)4–(ZnCl2)2}2–

Reduction of iron(II) octaethyltetrapyrazinoporphyrazine, FeIITPyzPzEt8, by zinc dust allowed the preparation of crystalline salt (PPN+)2{FeII(TPyzPzEt8)4–(ZnCl2)2}2– (1) (PPN+ is bis(triphenylphosphoranylidene)ammonium). Metal atom zinc transfers two electrons to FeIITPyzPzEt8 forming the {Fe(TPyzPzEt8)}2– dianions which coordinate two ZnCl2 units on the periphery of the TPyzPzEt8 macrocycle. Tetrahedral environment around the zinc(II) atoms is formed with the length of the Zn–N bonds of 2.071(7) Å with meso‐ and 2.304(8) Å with pyrazine nitrogen atoms of TPyzPzEt8. Optical and EPR spectra show the formation of diamagnetic tetraanionic {TPyzPzEt8}4– macrocycle in 1, and as a result, two‐electron reduction of FeIITPyzPzEt8 is centered exclusively on the macrocycle. According to DFT calculations for the {Fe(TPyzPzMe8)(ZnCl2)2}2– and {Fe(TPyzPzMe8)}2– dianions the reason of that is strongly increased electron affinity of the TPyzPzMe8 macrocycle at the coordination of two ZnCl2 units. Obviously, this situation is different from iron(II) phthalocyanine which shows metal‐centered first and second reduction.

Synthesis and crystal structure of new copper(II) metal complex: Noncovalent interactions and electrical conductance properties

[Cu(pydc)(apyz)(H2O)2] (1) (where pydcH2 = pyridine-2,6-dicarboxylic acid; apyz = 2- aminopyrazine) has been synthesized and characterized by elemental analysis, IR spectroscopy and single crystal X-ray diffraction techniques. Crystallographic analysis revealed that complex 1 has distorted octahedral geometry with pydcH2 coordinated as tridentate ligands to metal ion through two oxygen atoms of each carboxylate group, nitrogen atom of the pyridine ring and the auxiliary ligand pyrazine nitrogen atom form basal plane and apical positions are occupied by two oxygen atoms of water molecules. In addition, the coordination compounds are connected by a variety of non covalent interactions like OH … π, lone pair … π, π … π and hydrogen bonds. The evaluation of these noncovalent interactions is useful for rationalizing their influence in the crystal packing. In addition, electrical current measured at room temperature on thin film before and after annealed is in the order of 229 μA and 246 μA respectively with bias voltage 1 V.

Synthesis, structures and spectroscopic properties of some tin(IV) complexes of the 2-acetylpyrazine Schiff bases of S-methyl- and S-benzyldithiocarbazates

Tin(IV) complexes of formulae, [Sn(acpysme)(C6H5)2Cl], [Sn(acpysbz)(C6H5)2Cl], [Sn(acpysbz)(C6H5)Cl2] and [Sn(acpysbz)I3] (acpysme and acpysbz=anionic forms of the 2-acetylpyrazine Schiff bases of S-methyldithiocarbazate and S-benzyldithiocarbazate, respectively) have been synthesized and structurally characterized by a variety of physico-chemical techniques and X-ray diffraction measurements. In all these complexes the tin atom adopts a distorted octahedral geometry with the Schiff bases coordinating with the tin(IV) ion as uninegatively charged tridentate NNS chelating agents via one of the pyrazine nitrogen atoms, the azomethine nitrogen atom and the thiolate sulfur atom. In the [Sn(NNS)Ph2Cl] complexes, the three NNS donor atoms of the Schiff base and a chloride ion occupy equatorial positions whereas the two phenyl groups take up axial positions of a distorted octahedron. The complexes, [Sn(acapsbz)(Ph)Cl2] and [Sn(acapsme)I3] have also distorted octahedral configurations but in this case the halido ligands are in axial positions. The Schiff bases, Hacapsme and Hacapsbz and the complex, [Sn(acpysme)I3] exhibit strong cytotoxic activity against the human breast cancer cell lines, MDA-MB-231.

Delta chirality ruthenium ‘light-switch’ complexes can bind in the minor groove of DNA with five different binding modes

[Ru(phen)2(dppz)]2+ has been studied since the 1990s due to its ‘light-switch’ properties. It can be used as a luminescent DNA probe, with emission switched on through DNA binding. The luminescence observed is dependent on the solvent accessibility of the pyrazine nitrogen atoms, and therefore is sensitive to changes in both binding site of the cation and chromophore orientation. The compound is also chiral, and there are distinct differences between the enantiomers in terms of the emission behaviour when bound to a variety of DNA sequences. Whilst a number of binary DNA-complex X-ray crystal structures are available, most include the Λ enantiomer and there is very little structural information about binding of the Δ enantiomer. Here, we present the first X-ray crystal structure of a Δ enantiomer bound to well-matched DNA, in the absence of the other, Λ enantiomer. We show how the binding site observed here can be related to a more general pattern of motifs in the crystallographic literature and propose that the Δ enantiomer can bind with five different binding modes, offering a new hypothesis for the interpretation of solution data.

Synthesis and characterisation of new copper(II) coordination polymers constructed from pyrazine–tetrazole ligands with the formation of a water cluster

Three novel bis-tetrazole ligands (1–3) containing carboxylate functional groups on the tetrazole rings and a rigid pyrazine linker unit, for the construction of coordination polymers when coordinated to copper(II) ions, were synthesised and structurally characterised. The use of pyrazine as a rigid linker between the two tetrazole units was expected to increase the dimensionality of the solid phase polymeric network of the resulting copper(II)-containing compounds. X-ray structures of the ligands revealed the effect of the substitution position on the tetrazole ring of the ester/carboxylate groups. Higher solid phase dimensionality was successfully achieved as shown by the layered two-dimensional (2-D) coordination structure being formed when the pyrazine bis-tetrazole systems were reacted with copper(II) chloride, although not in the expected manner. There was no interaction between the pyrazine nitrogen atoms and the metal ion. Computational studies showed that this was probably due to the geometry, required by the copper ion, to be involved in the close packing between the layers. The 2-D coordination polymer based on the asymmetric substituted pyrazine bis-tetrazole, [Cu(4)(H2O)](H2O)2, was further connected into a three-dimensional (3-D) coordination network through hydrogen bonding between H2O molecules. These H2O molecules were connected as a unique 1-D chain throughout the structure.

Consecutive introduction of Ag(i)to an anionic homoleptic Co(iii) complex: variable Ag(i) coordination mode

Although the pyridine-2,6-diamide ligand is widely reported, coordination chemistry of the analogous pyrazine-2,6-diamide ligand has not been reported to date. To study the complexation behavior, we have synthesized N,N′-dibenzylpyrazine-2,6-dicarboxamide and the heterometallic complexes were in a stepwise manner. After dimerisation with Co(III) complexation, two ring nitrogen atoms are freely available. These two free pyrazine nitrogen atoms were studied for their coordination with Ag(I), resulting in three heterometallic complexes, C40H34AgCoN8O5, C42H38Ag3CoN10O11 and C42H53AgCoN9O13. The mode of coordination could be controlled by varying the metal to ligand ratio and varying the counter anion. Moreover, we found conditions that make the ligand to either coordinate or not coordinate to Ag+. Some of these complexes also display the rare organometallic (C–Ag) bond.

Spin Crossover, Reversible Redox, and Supramolecular Interactions in 3d Complexes of 4-(4-Pyridyl)-2,5-dipyrazyl-pyridine.

A new terpyridine-inspired terdentate ligand, 4-(4-pyridyl)-2,5-dipyrazyl-pyridine (py-pzpypz), featuring three "spare" nitrogen donors "out the back", has been used to synthesize five bis-ligand complexes, [M(II)(py-pzpypz)2]X2, where M = Mn with X = ClO4, or M = Fe, Co, Ni, and Zn with X = BF4. In contrast, when M = Cu(II), regardless of the M:L ratio employed, 1:1 M:L products were obtained: for X = BF4 a 1D chain {[Cu(II)(py-pzpypz)(DMF)2](BF4)2}n, and for X = Cl a monometallic complex [Cu(py-pzpypz)Cl2]. All seven complexes were structurally characterized, confirming the expected N6 coordination of the M(II) centers in all cases except Cu(II). Notably, a Jahn-Teller elongation is observed in the Co(II) complex, consistent with it being low spin at 100 K. The Cu(II) 1D chain complex has an N4O2 coordination sphere as in this case the "spare" pyridine donor out the back of the py-pzpypz ligand bridges to the next Cu(II) center in the chain, hence providing both a terdentate site and a monodentate pyridine to the next Cu(II) center, and the coordination sphere is completed by weak axial coordination by two DMF solvent molecules. The Cu(II) center in the monometallic complex has an N3Cl2 square pyramidal coordination sphere. In all cases, the noncoordinating, "spare", pyrazine nitrogen atoms are involved in interesting intermolecular interactions, including NPz-π interactions and nonclassical C-H···NPz hydrogen bonding. The Fe(II) complex is low spin as expected. Two polymorphs of the Co(II) complex were obtained, both of which showed gradual spin crossover, with a room temperature T1/2. Two reversible redox processes are observed for [Co(II)(py-pzpypz)2](BF4)2, with Em(M(I)/M(II)) = -0.63 V and Em(M(II)/M(III)) = +0.37 V, and a quasireversible redox process for [Fe(II)(py-pzpypz)2](BF4)2, with Em(M(II)/M(III)) = +1.26 V, versus 0.01 M AgNO3/Ag in MeCN. These potentials are shifted to significantly higher potentials (by ∼0.45 V) than the literature values for the corresponding Fe(II) and Co(II) complexes of the equivalent all-pyridine ligand, consistent with replacement of the two pyridine rings by two pyrazine rings significantly stabilizing the lower oxidation states.

Planar Cu2(ppz)2 Dimers as SBUs for Diverse Polyoxometalate-Based Metal Organic Frameworks

Five new polyoxometalate-based metal organic frameworks, [Cu4(ppz)4(PO4)]·[CuBr2] (1), [Cu4(ppz)4(MoO4)2(H2O)]·2H2O (2), [Cu(Hppz)(Mo2O7)] (3), [Cu2(ppz)2(Mo3O10)] (4), and [Cu6(ppz)6(PMo3VMo9VIO40)] (5) (Hppz = 2-(1H-pyrazol-3-yl)pyrazine), have been hydrothermally synthesized and fully characterized, in which a planar Cu2(ppz)2 dimer acts as a secondary building unit (SBU) and provides up to six potential binding sites. In virtue of the strong Jahn–Teller (JT) effect of Cu(II) ions, the potential binding sites in the Cu2(ppz)2 SBU can facilely be occupied by auxiliary oxygen-donor anions and/or outward pyrazine nitrogen atoms of neighboring SBUs. The auxiliary oxygen-donor anions in compounds 1–5 range from simple phosphate and molybdate, zonal Mo2O72– and Mo3O102– to a spherical three-electron reduced Keggin anion [PMo12O40]6–, respectively. Compound 1 contains an unprecedented 3D (4,6)-connected cationic open framework [Cu4(ppz)4(PO4)]+ with 1D channels filled by linear CuBr2– anions, where the Cu2(pp...

A highly fluorescent dinuclear silver(I) complex of pyrazine derivatives: Combined experimental and DFT/TD-DFT investigations

A dinuclear neutral silver(I) complex, [Ag2(Hpyzdc)2(μ-dmpyz)] (1) (H2pydc=pyrazine-2,3-dicarboxylic acid, dmpyz=2,3-dimethylpyrazine), has been synthesized and characterized by elemental analysis, IR spectroscopy, thermal analysis and single crystal X-ray diffraction. X-ray diffraction data have shown that the Hpydc ligands in 1 act as bidentate ligands via the pyrazine nitrogen and carboxylate oxygen atoms, and the further carboxylic group remains unbonded in the protonated form. Uncommon intermolecular interactions have been observed in the crystal structure, such as dihapto aromatic and intramolecular agostic interactions. DFT calculations have also supported the latterly mentioned agostic interaction. Complex 1 exhibits, in the solid state, strong fluorescence with two emission maxima in the visible region. TD-DFT calculations performed on the optimized structure in acetonitrile medium, modeled within PCM approach, have significantly quantified the experimental absorption profile and suggested that LLCT and MLLCT transitions are mainly responsible for the higher and lower energy fluorescences respectively.

Nine non-symmetric pyrazine-pyridine imide-based complexes: reversible redox and isolation of [MII/III(pypzca)2]0/+when M = Co, Fe

The non-symmetric imide ligand Hpypzca (N-(2-pyrazylcarbonyl)-2-pyridinecarboxamide) has been deliberately synthesised and used to produce nine first row transition metal complexes: [M(II)(pypzca)(2)], M = Zn, Cu, Ni, Co, Fe; [M(III)(pypzca)(2)]Y, M = Co and Y = BF(4), M = Fe and Y = ClO(4); [Cu(II)(pypzca)(H(2)O)(2)]BF(4), [Mn(II)(pypzca)(Cl)(2)]HNEt(3). These are the first deliberately prepared complexes of a non-symmetric imide ligand. X-ray crystal structures of [Cu(II)(pypzca)(2)]·H(2)O, [Co(II)(pypzca)(2)], [Co(III)(pypzca)(2)]BF(4), [Cu(II)(pypzca)(H(2)O)(2)]BF(4)·H(2)O and [Mn(II)(pypzca)Cl(2)]HNEt(3) show that each of the (pypzca)(-) ligands binds in a meridional fashion via the N(3) donors. In the first three complexes, two such ligands are bound such that the 'spare' pyrazine nitrogen atoms are positioned approximately orthogonally to one another and also to the imide oxygen atoms. In MeCN the [M(II/III)(pypzca)(2)](0/+) complexes, where M = Ni, Co or Fe, exhibit one reversible metal based M(II/III) process and two distinct, quasi-reversible ligand based reduction processes, the latter also observed for M(II) = Zn. [Mn(II)(pypzca)Cl(2)]HNEt(3) displays a quasi-reversible oxidation process in MeCN, along with several irreversible processes. Both copper(II) complexes show only irreversible processes. Variable temperature magnetic measurements show that [Fe(III)(pypzca)(2)]ClO(4) undergoes a gradual spin crossover from partially high spin at 298 K (3.00 BM) to fully low spin at 2 K (1.96 BM), and that [Co(II)(pypzca)(2)] remains high spin from 298 to 4 K. All of the complexes are weakly coloured, other than [Fe(II)(pypzca)(2)] which is dark purple and absorbs strongly in the visible region.