Synthesis, characterization and biological evaluation of a novel Cu(II) complex with the mixed ligands 2,6-pyridinedicarboxylic acid and 2-aminopyridine

A novel bridged binuclear Cu(II) complex with mixed ligands, di-μ-(2-aminopyridine(N,N′))-bis[(2,6-pyridinedicarboxylate)aquacopper(II)] tetrahydrate, formulated as [Cu(μ-ap)(dipic)(H₂O)]₂·4H₂O (1) (dipic = 2,6-pyridinedicarboxylate, ap = 2-aminopyridine), has been synthesized and characterized by elemental, spectral (IR and UV–Vis.), thermal analysis, magnetic measurements and single crystal X-ray diffraction analysis. The central Cu(II) ion resides on a centre of symmetry in a distorted square-pyramid coordination environment comprising of two N atoms, one from dipic and one from the ap ring, two carboxylate O atoms from dipic, and one O atom from water. Intermolecular N–HO and O–HO hydrogen bonds and π–π stacking interactions seem to be effective in the stabilization of the crystal structure. The free ligands and the complex were also evaluated for their antimicrobial and radical scavenging activities (DPPH = 1,1-diphenyl-2-picrylhydrazyl hydrate) using in vitro microdilution methods. Antimicrobial screening of the free ligands and their complex showed that the free ligands and the complex possess antifungal activity against Candida sp.     

Molybdenum(VI) network polymers based on anion–π interaction and hydrogen bonding: Synthesis, crystal structures and oxidation catalytic application

A crystallographic investigation of anion–π interactions and hydrogen bonds on the preferred structural motifs of molybdenum(VI) complexes has been carried out. Two molybdenum(VI) network polymers MoO₂F₄·(Hinca)₂ (1) and MoO₂F₃(H₂O)·(Hinpa) (2), where inca = isonicotinamide and inpa = isonipecotamide, have been synthesized, crystallographically characterized and successfully applied to alcohol oxidation reaction. Complex 1 crystallizes in the monoclinic space C2/c: a = 16.832(3) Å, b = 8.8189(15) Å, c = 12.568(2) Å, β = 118.929(3)°, V = 1560.1(5) Å³, Z = 4. Complex 2 crystallizes in the triclinic space P-1: a = 5.459(2) Å, b = 9.189(4) Å, c = 12.204(5) Å, α = 71.341(6)°, β = 81.712(7)°, γ = 77.705(7)°, V = 564.8(4) Å³, Z = 2. Complex 1 consists of hydrogen bonding and anion–π interactions, both of which are considered as important factors for controlling the geometric features and packing characteristics of the crystal structure. The geometry of the sandwich complex of [MoO₂F₄]²⁻ with two pyridine rings indicates that the anion–π interaction is an additive and provides a base for the design and synthesis of new complexes. For complex 2, the anions and the protonated inpa ligands form a 2D supramolecular network by four different types of hydrogen contacts (N–HF, N–HO, O–HF and O–HO). The catalytic ability of complexes 1 and 2 has also been evaluated by applying them to the oxidation of benzyl alcohol with TBHP as oxidant.     

Vibrational satellite of Na(3d ← 3s) dipole-forbidden transition in Na/CF4 mixture

Excitation spectra of Na fluorescence in mixtures with CF₄ display a new band shifted by the energy of one-vibrational quantum of the IR active ν₃-mode of CF₄ (1281 cm⁻¹) from Na 3d states. This band is attributed to a Na(3s)CF₄(ν₃ = 0) → Na(3d)CF₄(ν₃ = 1) transition and its intensity is explained by coupling with Na(4p)CF₄(v₃ = 0) resonance state which lies  180 cm⁻¹ below in energy. An analogous satellite of the Na 6p state combined with the same vibration and lying close to the Na 7p state is reported and discussed.     

Interligand interactions involved in the molecular recognition between copper(II) complexes and adenine or related purines

The available crystal structure information in the CSD database on ternary species prepared by the reaction of diverse copper(II) complexes (CuL) and purine, adenine and guanine or related purine derivatives is considered in order to deepen the intra-molecular interligand interactions affecting the molecular recognition patterns of the ‘metal complex + purine nucleobase’ and closely related systems. The degree of protonation and the possibilities of different tautomeric forms in the purine-like moieties are taken into account. The main conclusion is a general trend to form a CuN(purine-like) coordination bond which can be reinforced by an intra-molecular interligand H-bonding interaction. NH(purines)A (O or Cl acceptor) or NH(amino ligand L)O6(oxo-purines) are commonly observed. In addition, selected examples revealed that the presence of a variety of non-coordinating groups in L or in the purine-like nucleobases can significantly influence the structurally observed molecular recognition pattern. Moreover, examples are known where binuclear cores of the types Cu^II₂(μ₂-N3,N9-adeninate)₄(aqua)₂ or Cu^I₂(μ₂-N3,N9-adeninate)₂(aqua)₂ recognise CuL chelates by means of the expectable pattern (CuN7 coordination bond + N6HO(L) interaction).     

C–HPt(II) interaction-controlled self-assembly and photophysics of chiral bis(pyrrol-2-ylmethyleneamino)cyclohexane platinum(II) complexes

Reaction of (R,R)-(−)- and (S,S)-(+)-1,2-bis(pyrrol-2-ylmethyleneamino)cyclohexane with K₂PtCl₄ afforded chiral, neutral platinum(II) Schiff base complexes of (R,R)-PtL and (S,S)-PtL with high yields. The rare C–HPt(II) intermolecular interaction was found to show considerable strength and directionality for controlling M and P helical supramolecular architectures of (R,R)-PtL and (S,S)-PtL, respectively, in crystal lattices. More importantly, the open square-planar geometry of platinum(II) complexes allows axial C–HPt(II) interaction, resulting in the ³(ππ^*) excited state with some mixing of the Pt(II) metal character observed both in concentrated solutions and in the solid state at room temperature.     

Specific crystal structure of poly(3-hydroxybutyrate) thin films studied by infrared reflection–absorption spectroscopy

Infrared reflection–absorption (IR-RAS) and transmission spectra were measured for poly(3-hydroxybutyrate) (PHB) thin films to explore its specific crystal structure in the surface region. As IR-RAS is sensitive to the vibration mode of perpendicular orientation of the surface, differences between IR-RAS and transmission spectra indicate an orientation of the lamella structure in the surface of PHB thin films. The relative intensity of the crystalline CO stretching band in the IR-RAS spectrum is significantly weaker than that in the transmission spectrum. It may be concluded that the transient dipole moment of the CO stretching mode of the crystalline state is not oriented perpendicular but nearly parallel to the substrate surface. On the other hand, the relative intensity of the band at 3009 cm⁻¹ due to the C–H stretching mode of the C–HOC hydrogen bonding is similar between the IR-RAS and transmission spectra, suggesting that the C–H bond is oriented neither perpendicular nor parallel to the substrate surface but in an intermediate direction. Since the CO group of the C–HOC hydrogen bonding is oriented nearly parallel to the surface and its C–H group is in the intermediate direction, it is very likely that the C–HOC hydrogen bonding has a somewhat bent structure. These results are in good agreement with our previous conclusion that the C–HOC hydrogen bonding of PHB exists along the a-axis (not the b-axis) between the CH₃ group of one helix and the CO group of another helix.     

Competition between non-classical and classical hydrogen bonded sites in [BH3CN]: Spectral, energetic, structural and electronic features

Interaction of the salt (Ph₃PNPPh₃)BH₃CN with the various OH and NH proton donors in low polar media was studied by variable temperature (200–290 K) IR spectroscopy and theoretically by DFT calculations. The formation of two types of complexes containing non-classical dihydrogen bond to the hydride hydrogen (DHB) and classical hydrogen bond (HB) to nitrogen lone pair was shown in solution. The 1:1 complexes of both types (XHH and XHN) coexist in the presence of equimolar amount of proton donor. The addition of excess XH-acid leads to the increase of the classical HB content and appearance of the 1:2 complexes, where two basic sites work simultaneously. The structure, spectral characteristics, energy and electron redistribution were studied by DFT (B3LYP) method. The comparison DHB parameters of [BH₃CN]⁻ with those of the unsubstituted analogue [BH₄]⁻ allowed analyzing the electronic effects of the CN group on the basic properties of boron hydride moiety. The electronic influence of the BH₃ group on CN⁻HX hydrogen bond was also established by comparison with the corresponding classical HB to the CN⁻ anion.     

Influence of hydration on the protomeric tautomerism in selenium analogue of methimazole: A computational chemistry study

Hydrogen bond assisted proton transfer reactions were investigated in 3-methyl-1H-imidazole-2(3H)-selone (MSeI) and 1H-imidazole-2(3H)-selone (SeI) at B3LYP/6-311++G(2d,2p) level of theory. The B3LYP results predict that the direct proton transfer process in MSeI and SeI is more difficult than the water-assisted one. The results also show that the selone complexes are more stable than corresponding selenol ones. Interaction energies for a single NHSe hydrogen bond in dimers MSeI and SeI are −31.3 and −32.7 kJ/mol, respectively. ZPE-corrected binding energies in the self-association complexes of the MSeI and SeI are greater than the water-associated complexes. The small negative value of H(r) obtained by AIM analysis at B3LYP/6-311++G(2d,2p) level reveals some contribution of sharing interaction (partially covalent) to the SeHN bond in dimers of the MSeI and SeI. AIM data also reveal the partially covalent nature of SeH6 interaction and electrostatic nature of OH5 interaction in water-associated complexes. Results of charge analysis show that the selenium analogue of the methimazole is more nucleophilic than the methimazole. Our results confirm that the selenium analogue of methimazole can exist as a zwitterionic form.     

(1,4-dabH)2MnSnS4: The first thiostannate with integrated Mn ions in an anionic chain structure

The new thiostannate (1,4-dabH)₂MnSnS₄ (1,4-dab = 1,4-diaminobutane) was synthesized under solvothermal conditions. The compound crystallizes in the non-centrosymmetric space group Fdd2 with a = 22.8124(15) Å, b = 24.7887(16) Å, c = 6.4153(6) Å, Z = 8, and V = 3627.8(5) Å³. The structure consists of one-dimensional straight anionic chains composed of alternating SnS₄ and MnS₄ tetrahedra sharing common edges. The chains are directed along [001] and are surrounded by the organic cations which form undulated chains along [100] by strong intermolecular N–HN hydrogen bonding interactions. Several SH contacts suggest weak interactions between the anionic chains and the cations. The band gap amounts to 2.9 eV indicating that the compound is a photo-conductor. The compound is stable up to about 190 °C and decomposes in two distinct steps above this temperature.     

Syntheses, crystal structures, spectral and thermal analysis and biological activities of copper(II)-pyridine-2,5-dicarboxylate complexes with 4-methylimidazole, imidazole, and 3,4-dimethylpyridine

In this study, three novel Cu(II)-pyridine-2,5-dicarboxylate (pydc) complexes with 4-methylimidazole (4-Meim), [Cu(pydc)(H₂O)(4-Meim)₂]·H₂O (1), imidazole (im), {[Cu(μ-pydc)(im)₂]·2H₂O}_n (2), and 3,4-dimethylpyridine (dmpy), [Cu(μ-pydc)(H₂O)(dmpy)]_n (3) have been synthesized. Elemental and thermal analyses, magnetic susceptibilities, IR and UV/vis spectroscopic studies have been performed to characterize the complexes. The molecular structures of mononuclear (1) and polynuclear (2 and 3) complexes have been determined by the single crystal X-ray diffraction technique. In 1 and 2, Cu(II) ions have distorted square planer geometry, while 3 has distorted octahedral coordination. The pyridine-2,5-dicarboxylate exhibits three different coordination modes namely bidentate (1), tridentate (2) and tetradentate (3). The complex 1 is further constructed to form three-dimensional framework by hydrogen bonding, C–Hπ and ππ stacking interactions. The adjacent chains of 2 and 3 are then mutually linked via hydrogen bonding, ππ and C–Hπ interactions, which are further assembled to form three-dimensional framework. 1 exhibits the magnetic moment value of 1.70 BM, which corresponds to one of the unpaired electron, while the polynuclear complexes 2 and 3 exhibit 1.58 and 1.46 BM, which is lower than the spin only value for one unpaired electron, indicates to antiferromagnetic effect. The first thermal decomposition process of all the complexes is endothermic dehydration. This stage is followed by partial (or complete) decomposition of the neutral and pydc ligands. In the later stage, the remained organic residue exothermically burns. The final decomposition products which identified by IR spectroscopy were the CuO.     

Molecular DFT structure and packing effect of thiodipropionic and dithiodiglycolic acids and salts

Molecular and periodic DFT structure calculations of thiodipropionic and dithiodiglycolic acids, S_n[(CH₂)(COOR)]₂ (n = 1,2, R = H, Na), were performed. Computed structures were analyzed and compared to the experimental data (a C_s conformation is favored in solution than C₂ in solid state). Four close and low-energy optimized conformations were analyzed: C_2v, C₂, C_s and C₁. Small changes in the conformation stability (ΔG) and symmetry group were observed in polar medium. Periodic DFT-GGA approaches have been performed to determine the importance of weak interaction upon the crystal structure of the thiodipropionic acid, e.g., S–H and/or O–H hydrogen bonding. More SH and OH dispersed bands were observed in the optimized structure. Using a full analysis of the DOS of O–H or S–H bonding contributions, a notable interlayer bonding in the parent structure was revealed. Therefore, the presence of such weak interaction ONa⁺ or OH may thus change the point group symmetry of the crystal upon packing effect.     

Ba2In2O4(OH)2: Proton sites, disorder and vibrational properties

The structure of Ba₂In₂O₄(OH)₂ is analysed by the explicit full optimization of a large number of possible proton arrangements using periodic density functional theory. It is shown that the experimental assignments in which protons appear to be located at high symmetry positions with unphysical bond lengths do not correspond to minima on the potential energy hypersurface. The apparent sites are averages of a number of possible proton locations involving a set of possible local structural environments in which the internuclear separations are more realistic. Such problems with structural refinements are common where profile refinement programs place the atoms at the average position due to dynamic and/or static disorder. Thus while the calculations support a previous neutron diffraction analysis of the structure in that the average structure contains two different proton sites, they also reveal substantial information about the local environments of the protons. In all optimizations, the protons moved from the average positions suggested in the neutron diffraction study with calculated O–H and OHO distances consistent with those observed in other oxides. The energies of different proton distributions vary significantly so the protons are not randomly distributed. We also present an analysis of the vibrational properties of the O–H bonds. Since the strength of the hydrogen bonds is closely related to the local structural environments of the protons, a range of vibrational frequencies is obtained providing a prediction of the vibrational spectra. In O–HO linkages, O–H stretching modes soften with increasing HO hydrogen bond strength, while the in-plane and out-of-plane bending or libration modes stiffen. Together, our results show how modern theoretical methods can provide a clearer understanding of the structure and dynamics of a complex inorganic material.     

Structural role of hydrogen bond networks in amino acid–acid systems. (I) The network with highly polarizable OHO hydrogen bonds in sarcosine–methanesulfonic acid (2:1) crystal

The sarcosine–methanesulfonic acid (2:1) crystal was selected for examination of two problems: relations between different components of the amino acid–acid hydrogen bond network and a role of very strong and highly polarizable OHO hydrogen bond in the main structural units of the crystal: sarcosinium–sarcosine dimers (complexes). Our observations are based on phase transitions of the crystal monitored by DSC, X-ray diffraction and temperature evolutions of selected bands of IR spectra. Our experimental and DFT results provide information on the potential energy profile of the OHO proton and its evolution with temperature. The OO distance of the primary hydrogen bond remains almost unchanged and its proton is strongly delocalized and sensitive on neighbour NHO hydrogen bond. We propose a possible mechanism of the phase transitions and coupling between νCO vibrations of the carboxyl group and moving of the proton in neighbour OHO hydrogen bridge.     

The catalytic effects of various third molecules on reaction channels of weakly bound complex CO2HF systems in the vapor phase

In this investigation, reaction channels of weakly bound complexes CO₂HF, CO₂HFH₂O, CO₂HFNH₃, CO₂HFCH₃OH, CO₂HFNH₂CH₃, CO₂HFNH(CH₃)₂ and CO₂HFN(CH₃)₃ systems were studied at the B3LYP/6-311++G(3df,2pd) level. The conformers of syn-fluoroformic acid or syn-fluoroformic acid plus a third molecule (H₂O, NH₃, CH₃OH, NH₂CH₃, NH(CH₃)₂ or N(CH₃)₃) were found to be more stable than the conformers of the related anti-fluoroformic acid or anti-fluoroformic acid plus a third molecule (H₂O, NH₃, CH₃OH, NH₂CH₃, NH(CH₃)₂ or N(CH₃)₃). However, the weakly bound complexes were found to be more stable than either the related syn- and anti- type fluoroformic acid or the acid plus third molecule (H₂O, NH₃, CH₃OH, NH₂CH₃, NH(CH₃)₂ or N(CH₃)₃) conformers. They decomposed into CO₂+HF, CO₂+H₃OF, CO₂+NH₄F, CO₂+(CH₃)OH₂F, CO₂+NH₃(CH₃)F, CO₂+NH₂(CH₃)₂F, or CO₂+NH(CH₃)₃F combined molecular systems. The weakly bound complexes have seven reaction channels, each of which includes weakly bound complexes and their related systems. Moreover, each reaction channel includes two transition state structures. The transition state between the weakly bound complex and anti-fluoroformic acid type structure (T₁₃) is significantly higher than that of internal rotation (T₂₃) between the syn- and anti-FCO₂H (or FCO₂HH₂O, FCO₂HNH₃, FCO₂HCH₃OH, FCO₂HNH₂CH₃, FCO₂HNH(CH₃)₂, or FCO₂HN(CH₃)₃) structures. However, adding the third molecule H₂O, NH₃, CH₃OH, NH₂CH₃, NH(CH₃)₂ or N(CH₃)₃ can significantly reduce the activation energy of T₁₃. The catalytic strengths of the third molecules are predicted to follow the order H₂O<NH₃<CH₃OH<.NH₂CH₃<NH(CH₃)₂<N(CH₃)₃.     

Fermi resonance and strong anharmonic effects in the absorption spectra of the ν-OH (ν-OD) vibration of solid H- and D-benzoic acid

The vibrational spectra of polycrystalline benzoic acid (BA) and its deuterated derivative were studied over the wide frequency region 4000–10 cm⁻¹ by IR and Raman methods. A theoretical analysis of the hydrogen bond frequency region and calculations at the B3LYP/6-311++G(2d, 2p) level for the benzoic acid cyclic dimer in the gas phase were made. In order to study the dynamics of proton transfer two formalisms were applied: Car–Parrinello Molecular Dynamics (CPMD) and Path Integrals Molecular Dynamics (PIMD). It was shown that the experimentally observed very broad ν-OH band absorption is the result of complex anharmonic interaction: Fermi resonance between the OH-stretching and bending vibrations and strong interaction of the ν-OH stretching with the low frequency phonons. The theoretical analysis in the framework of such an approach gave a good correlation with experiment. From the CPMD calculations it was confirmed that the O–HO bridge is not rigid, with the OO distance being described by a large amplitude motion. For the benzoic acid dimer we observed stepwise (asynchronous) proton transfer.     

Theoretical study of the interaction of a proton with the O, F and Cl atoms of enflurane (CHFCl–CF2–O–CHF2)

Ab initio MP2 and density functional B3LYP calculations were performed to investigate the interaction of a proton with the O, F and Cl atoms of enflurane (CHFCl–CF₂–O–CHF₂) in the gas phase. The study included the optimized structures, proton affinities, interactions energies and thermodynamic properties of protonated enflurane. The proton affinities (PAs) of the O and Cl atoms are 154.5 and 139.8 kcal mol⁻¹, respectively, whereas PAs of five of the fluorine atoms are between 143.6 and 165.5 kcal mol⁻¹ (MP2 results). In contrast to protonation at the O and Cl atoms, protonation at each of the F atoms of enflurane reveals a striking result, it leads to a cleavage of the C–F bond and formation of an ion–dipole complex between the enfluranyl cation and neutral hydrogen fluoride. The [(enfluranyl)⁺FH] complexes are weakly bound, the SAPT-calculated interaction energy varies between −12.5 and −11.7 kcal mol⁻¹. The long range attraction in these complexes is dominated by the electrostatic term (70%), whereas the induction and dispersion components contribute by about 15% each. Protonation at the chlorine atom of enflurane does not lead to a cleavage of the C–Cl bond. For the O-protonated enflurane the results from the natural bond orbital analysis (NBO) are discussed in details.     

Crystal structure of olanzapine and its solvates. Part 3. Two and three-component solvates with water, ethanol, butan-2-ol and dichloromethane

Crystalline solvates of olanzapine (1), 2-methyl-4-(4-methyl-1-piperazinyl)-10H-thieno[2,3-b][1,5]benzodiazepine, have been characterized by an X-ray analysis and thermal (DSC) data. Crystallization of 1 from ethanol gives a solid containing both water and ethanol molecules; the solvate 1 · H₂O · EtOH (2:2:1) is monoclinic with the space group P2₁/c and the unit-cell volume V = 3752.8(12) Å³. Butan-2-ol forms with 1 solvate which is also a three-component phase, 1 · H₂O · BuOH, but its stoichiometry is different (1:1:1). The space group for this crystal is P2₁/c and the unit-cell volume V = 2216.5(7) Å³. Crystalline olanzapine dichloromethane solvate (2:1), 1 · CH₂Cl₂, is triclinic with the space group .The characteristic feature of all crystal structures is presence of a pair of olanzapine molecules which form dimer stabilized by multiple weak C–Hπ interactions between the N-methylpiperazine fragment and the phenyl / thiophene systems. Theoretical calculations have been performed indicating that the total C–Hπ binding energy is about 8 kcal mol⁻¹. In the crystal structure, the self-assembled olanzapine molecular dimers are arranged into parallel crystal planes. Packing of the layers proceeds in two ways in which structural motives are replicated by (i) perpendicular translation forming columns, and (ii) rotation around the twofold screw axis (parallel to the layer).     

Reaction of diacetylmonoxime with morpholine N-thiohydrazide in the absence and in presence of a metal ion: Facile synthesis of a thiadiazole derivative with non-bonded SS interaction

The condensation of diacetylmonoxime (damnx) with morpholine N-thiohydrazide (mth) in 1:1 molar ratio in ethanol (16 h) afforded a nitrogen–sulfur zwitterionic heterocyclic compound, N-(3,4-dimethyl-1,2,5-thiadiazole-2-ium-2-yl)morpholine-4-carbothioate (dtmc). However, the same reaction in presence of [Zn(OAc)₂]·2H₂O in ethanol under gentle reflux on (3 h) yielded the zinc complex, [Zn(Hdammthiol)(OAc)(H₂O)]·H₂O, where H₂dammthiol (H₂L²) is the thiol form of tridentate NNS donor thiohydrazone ligand, diacetylmonoxime morpholine N-thiohydrazone (Hdammth). Both the nitrogen–sulfur heterocyclic compound and the zinc complex have been characterized by elemental analyses, spectroscopy (IR, UV–Vis, ¹H NMR and ¹³C NMR) and single crystal X-ray crystallography. It is noteworthy that the heterocyclic compound shows SS interaction with distance 2.738 Å in its planar conformation. The heterocyclic compound forms two dimensional supramolecular sheets through C–HO and ππ interactions while the zinc complex, with distorted square pyramidal geometry, forms 1D supramolecular chain. A mechanism has been proposed for the formation of nitrogen–sulfur heterocyclic compound.     

Unimolecular chemistry of metastable dimethyl isophthalate radical cations

The MS/MS spectrum of the metastable molecular ions of dimethyl isophthalate 1 differs from that of the isomeric dimethyl terephthalate 2 by the observation of, inter alia, a quite intense loss of C,H₂,O ascribed to formaldehyde. Results obtained using a combination of mass spectrometry techniques suggest that this process could consist of an isomerization reaction of the molecular ion into an ion–neutral complex (INC) linking a benzoyl radical and neutral formaldehyde to a proton [ArCOHOCH₂]⁺. Within the complex, a proton transfer catalyzed by formaldehyde occurs resulting in the production of an ionized cyclohexadienylidene methanone (ketene) structure.     

Synthesis, crystal structures and magnetic properties of trinuclear oxo-centered homo- and mixed-valence manganese pivalate complexes with imidazole (Im) and 1-methylimidazole (1-MeIm): and

Two new μ₃-oxo-centered trinuclear manganese complexes, one of them a homo-valence (1) pivalate complex and the other a mixed-valence (2) pivalate complex (where Im = imidazole, 1-MeIm = 1-methylimidazole), have been synthesized and characterized by IR spectroscopy, thermogravimetric analysis, X-ray crystallography and magnetochemistry. Complexes 1 and 2 are μ₃-oxo-trinuclear compounds with the three manganese atoms bridged by six pivalate groups. At each axial position there is an Im (1) or 1-MeIm (2) molecule. In both compounds, the manganese coordination geometry is slightly distorted octahedral, consisting of the oxygen of the central triangle, four oxygen atoms from bridging pivalate ligands, and a terminal Im or 1-MeIm nitrogen atom. The crystal packing of 1 involves hydrogen bonding between complex cations [Mn₃O(Piv)₆(Im)₃]⁺ and outersphere pivalate ions, whereas in compound 2 interactions of the C–Hπ type, formed by both the aromatic and methyl C–H groups of 1-MeIm molecules, are present. Magnetic studies reveal that both compounds represent antiferromagnetically coupled, spin-frustrated triangular systems exhibiting weak to moderate exchange coupling constants.