Compartmental Schiff Base Ligand Research Articles

Magnetic Interaction Affecting the Zero-Field Single-Molecule Magnet Behaviors in Isomorphic {NiII2DyIII2} and {CoII2DyIII2} Tetranuclear Complexes.

Great interest is being shown in investigating magnetic interactions that efficiently influence lanthanide single-molecule magnet behavior. A series of heterometallic complexes [M2Ln2(Hhms)2(CH3COO)6(CH3OH)2(H2O)2]·(NO3)2 (M = NiII, Ln = DyIII (1), GdIII (2), and YIII (3); M = CoII, Ln = DyIII (4), GdIII (5), and YIII (6)) have been prepared with a compartmental Schiff-base ligand, 1-(2-hydroxy-3-methoxybenzylidene)-semicarbazide (H2hms), featuring a zigzag-shaped MII-LnIII-LnIII-MII metallic core arrangement. In complexes 1-6, a unique monophenoxo/diacetate asymmetric bridging connects MII ion with LnIII ion, and four acetates bridge two LnIII ions where acetates play essential roles as coligand in generating the tetranuclear units. Magnetic studies reveal the presence of predominant ferromagnetic coupling in DyIII and GdIII derivatives, and slow relaxation of magnetization is observed for {Ni2IIDy2III} and {CoII2DyIII2} with an energy barrier of 16.0 K for {Ni2IIDy2III} and 6.7 K for {CoII2DyIII2} under zero static field. Compared with the analogue {CoII2DyIII2}, the {Ni2IIDy2III} shows longer relaxation time and an absence of the quantum tunnelling of the magnetization (QTM) at low temperatures. Ab initio calculations suggest that the zero-field QTM of {Ni2IIDy2III} is effectively interrupted thanks to the ferromagnetic exchange coupling generated between NiII and DyIII ions. The presence of ferromagnetic exchange between NiII and DyIII ions is more conducive to zero-field single-molecule magnet behaviors than in isomorphic {CoII2DyIII2} where the exchange is antiferromagnetic.

A novel compartmental Schiff base ligand as a fluorescence chemosensor : Microscopic to macroscopic detection of ZnII acetate

A novel compartmental Schiff base ligand as a fluorescence chemosensor : Microscopic to macroscopic detection of ZnII acetate

Syntheses, X-ray Crystal Structures, Photoluminescence Properties, Antimicrobial Activities and Hirshfeld Surface of Two New Cd(II) Azide/Thiocyanate Linked Coordination Polymers

The reaction of cadmium(II) acetate salts with multisite coordinated compartmental Schiff base ligand N,N'-Bis(3-methoxysalicylidenimino)-1,3-diaminopropane (H2L1) in presence of co-lingand azido/thiocyanato afforded two new coordination polymers {Cd-4(N-3)(4)(L-1)(2)]H2O}(n) (1), Cd-4(SCN)(4)(L-1)(2)](n) (2). The obtained compounds, 1 and 2 are 1D and 2D coordination polymers respectively and they have been characterized by IR spectroscopy, UV-vis spectroscopy, elemental analysis, and single-crystal X-ray diffraction. The variation in the extended forms of 1 and 2 is governed by the kind of co-ligands utilized in the reaction. The complete structural study reveals that, in both cases the fully deprotonated ligand L-1](2-) has utilized all six potential coordination sites to hold a pair of Cd(II) ions. Moreover, N-3](-) in 1 is coordinating to metal atom by both trans end-to-end (EE mu-1,3) and end-on (EO or mu-1,1) mode and SCN](-) is showing only end-to-end (EE mu-1,3) coordination mode in 2. The photo luminescent properties and antimicrobial activities of the compounds 1 and 2 were investigated and discussed in details. Upon irradiation with UV light Cd(II) polymeric compounds 1-2 exhibit deep blue emissions of 448-451 nm subjected to dimethyl sulfoxide solution due to pi ->pi* intraligand fluorescence. Apart from, as a complementary revelation, intermolecular interactions with respect to percentages of hydrogen bonding in the crystal structures of two Cd(II) polymeric compounds were quantified by Hirshfeld surface and fingerprint plots analysis.

Three series of heterometallic NiII-LnIII Schiff base complexes: synthesis, crystal structures and magnetic characterization.

Three series of NiII-LnIII complexes were synthesized with the general formulae [(μ3-CO3)2{Ni(HL)(CH3-CH2OH)Ln(CH3COO)}2]·2CH3CH2OH (1-6) (Ln = Tb (1), Dy (2), Ho (3), Er (4), Tm (5), Yb (6); H3L = N,N'-bis(3-methoxysalicylidene)-1,3-diamino-2-prop-anol), [Ni(HL)Ln(dbm)3]·CH3OH2·2CH2Cl2 (7-10) (Ln = Tb (7), Eu (8), Gd (9), Ho (10); Hdbm = 1,3-diphenyl-1,3-propanedione) and [Ni(HL)(H2O)(tfa)Ln(hfac)2] (11-15) (Ln = Tb (11), Dy (12), Eu (13), Gd (14), Ho (15); Hhfac = 1,1,1,5,5,5-hexafluoropentane-2,4-dione, tfa- = trifluoroacetate) using compartmental Schiff base ligands in conjunction with auxiliary ligands. For the NiLn series, the tetranuclear structure could be considered as two NiII-LnIII dinuclear subunits bridged by two carbonates derived from atmospheric carbon dioxide. The LnIII ions of complexes 1-6 were octa-coordinated with distorted triangular dodecahedral geometry, while the LnIII ions of the dinuclear complexes 7-15 were nona-coordinated with distorted muffin geometry. The magnetic properties of the three series complexes were studied using dc and ac magnetic measurements. For the NiII-GdIII complexes, the dc magnetic susceptibility measurements suggested the existence of the anticipated ferromagnetic interaction between NiII and GdIII ions. The fitting of the χMT vs. T data processed by PHI software provided the parameters g = 2.08 (J = +0.87 cm-1) for 9 and g = 2.02 (J = +1.83 cm-1) for 14. The interaction exchange was magneto-structurally correlated to the Ni-O-Gd angle (α) and Ni(μ-O)Gd dihedral angle (β). With an applied dc field, complexes 1 (Tb), 2 (Dy), 7 (Tb) and 12 (Dy) exhibited single magnetic relaxation with SMM parameters of Ueff/k = 13.60 K, 11.52 K, 7.69 K and 5.14 K, respectively. Analysis of the Cole-Cole plots for complexes 2 and 7 suggested that a single relaxation process was mainly involved in the relaxation process, with α values in the range of 0.37-0.17 and 0.14-0.11, respectively.

Syntheses, structures, and magnetic properties of a family of end-on azido-bridged CuII-LnIII complexes.

The reaction of Cu(valdmpn) (H2valdmpn = N,N'-bis-(3-methoxysalicylidene)-1,3-diamino-2,2-dimethylpropane), LnCl3·nH2O (Ln = La(1), Ce (2), Pr(3), Nd(4), Sm(5), Eu(6), Gd(7), Tb(8), Dy(9), Ho(10), Er(11), Tm(12), Yb(13), Lu(14)) and NaN3 in methanol led to a whole series of heterometallic CuII-LnIII complexes. The basic structural components of these complexes are the [CuII(valdmpn)LnIII] units with a compartmental Schiff-base ligand. These [CuIILnIII] units were then further connected by the end-on (EO) azides between the Ln3+ centers to form tetranuclear {[CuLn](μ-N3)n[LnCu]} motifs, where n is 3 for the complexes of larger radii lanthanides (1CuLa to 5CuSm) and 2 for the complexes of smaller radii lanthanides (6CuEu to 14CuLu). While compounds 6CuEu to 14CuLu remain isolated tetranuclear clusters, compounds 1CuLa to 5CuSm are one-dimensional chains where tetranuclear motifs are further connected by end-to-end (EE) azides between CuII and LnIII centers. Direct current (dc) magnetic susceptibilities have been measured in the range of 1.8-300 K for all complexes, revealing the different nature of magnetic interactions between the spin centers. Among them, dominant ferromagnetic interactions were found in compounds 7CuGd, 8CuTb and 9CuDy. Alternating current (ac) magnetic measurements performed on 8CuTb, 9CuDy, and 10CuHo demonstrated the presence of slow magnetic relaxation under zero applied dc field. The spin relaxation barrier Ueff was determined to be 19.54 cm-1 (28.12 K) and 10.34 cm-1 (14.87 K) for compounds 8CuTb and 9CuDy. The SMM behavior of 8CuTb was further confirmed by the presence of magnetic hysteresis loops; while no hysteresis loop was observed for 9CuDy and 10CuHo. These results demonstrated that azido-bridged copper(ii)-lanthanide(iii) complexes could be synthesized successfully despite the generally weak azido-lanthanide interaction.

Synthesis, structural characterization and DFT calculation on a square-planar Ni(II) complex of a compartmental Schiff base ligand

Reaction of a symmetric compartmental Schiff-base ligand, (H2L) with nickel(II) perchlorate hexahydrate in 1:1 M ratio in methanol gives rise to a mononuclear nickel(II) compound, NiL (1). The compound has been characterized by C, H, N microanalyses and UV–Vis spectra. The single crystal X-ray diffraction studies reveal a square planar geometry around the Ni(II) center. The compound crystallizes in monoclinic system with space group C2/c with a = 21.6425(6), b = 9.9481(3), c = 13.1958(4) Å, β = 107.728(2)°, V = 2706.16(14) Å3 and Z = 4. Ground state DFT optimization and TDDFT calculations on the ligand and complex were performed to get their UV–Vis spectral pattern.

Dinuclear Cu(II) complexes of compartmental Schiff base ligands formed from unsymmetrical tripodal amines of varying arm lengths: Crystal structure of [Cu2L1](ClO4)2 and theoretical studies

Three new dinuclear copper complexes were synthesized via condensation reaction of three new unsymmetrical N-capped tripodal amines and 2,6-diformyl-4-methylphenol, in the presence of copper(II) perchlorate. The solid-state structure of the dinuclear complex, [Cu2L1](ClO4)2, has been determined by X-ray crystallography, showing that the CuII centers have distorted square-pyramidal geometry with N3O2 coordination. The copper (II) ions are bridged by phenolic and hydroxyalkyl groups when in both cases, deprotonation of the hydrogen atoms of the OH groups occurs. The distance between the copper atoms is 3.062 Å. This compound consists of the dication [Cu2L1]2+ and two ClO4− anions in which one of ClO4− groups has a week interaction with one of the Cu atoms. All complexes were characterized by a variety of physico-chemical techniques such as elemental analyses, IR, mass spectra, conductivity measurements and electronic spectral studies. Computational investigation of mentioned binuclear Cu(II) complexes was done by using M062X method with LANL2DZ basis set in vacuo.

Synthesis, crystal structures and Hirshfeld surface analyses of two new Salen type nickel/sodium heteronuclear complexes

Two new heteronuclear Nickel(II)/Sodium(I) complexes of a side-off compartmental Schiff base ligand were synthesized and characterized by spectroscopic methods. Crystal structures of both of the complexes were also obtained. The Schiff base ligand was synthesized from the condensation of meso-1,2-diphenyl-1,2-ethylenediamine with 2-hydroxy-3-methoxybenzaldehyde. In both of the complexes the Ni(II) ion is coordinated to the inner N2O2 coordination sphere with square-planar geometry and the Na(I) ion is coordinated to the outer O2O2′ coordination sphere. In Complex (1) with general formula [Ni(L)Na(CH3OH)(ClO4)] the sodium ion is seven coordinated while in (2) with general formula [{Ni(L)Na(OH2)}2(μ-Ni(CN)4)] the sodium ion is six coordinated. Intermolecular interactions in two studied complexes were analyzed using 3D Hirshfeld surfaces and corresponding 2D fingerprint plots. This analysis showed that the H … H and C … H/H … C contacts for both structures (altogether 67.5% of total Hirshfeld surface area for (1) and 77.6% for (2)) and the O … H/H … O (24.2%) for (1) and the N … H/H … N (8.1%) contacts for (2) were the characteristic intermolecular contacts in the related crystal structures.

Unique mononuclear Mn(II) complexes of an end-off compartmental Schiff base ligand: experimental and theoretical studies on their bio-relevant catalytic promiscuity.

Three new mononuclear manganese(ii) complexes, namely [Mn(HL)2]·2ClO4 (1), [Mn(HL)(N(CN)2)(H2O)2]·ClO4 (2) and [Mn(HL)(SCN)2] (3) [LH = 4-tert-butyl-2,6-bis-[(2-pyridin-2-yl-ethylimino)-methyl]-phenol], have been synthesized and structurally characterized. An "end-off" compartmental ligand (LH) possesses two symmetrical compartments with N2O binding sites but accommodates only one manganese atom instead of two due to the protonation of the imine nitrogen of one compartment. Although all three complexes are mononuclear, complex 1 is unique as it has a 1 : 2 metal to ligand stoichiometry. The catalytic promiscuity of complexes 1-3 in terms of two different bio-relevant catalytic activities namely catecholase and phenoxazinone synthase has been thoroughly investigated. EPR and cyclic voltametric studies reveal that radical formation rather than metal centered redox participation is responsible for their catecholase-like and phenoxazinone synthase-like catalytic activity. A computational approach suggests that imine bond bound radical generation rather than phenoxo radical formation is most likely responsible for the oxidizing properties of the complexes.

Ligand centered radical pathway in catechol oxidase activity with a trinuclear zinc-based model: Synthesis, structural characterization and luminescence properties

A new trinuclear zinc(II) complex, [Zn3(L)(NCS)2](NO3)2·CH3OH·H2O (1), of a (N,O)-donor compartmental Schiff base ligand (H2L=N,N′-bis(3-methoxysalicylidene)-1,3-diamino-2-propanol), has been synthesized in crystalline phase. The zinc(II) complex has been characterized by elemental analysis, IR spectroscopy, UV–Vis spectroscopy, powder X-ray diffraction study (PXRD), 1H NMR, EI mass spectrometry and thermogravimetric analysis. PXRD revealed that 1 crystallizes in P−1 space group with a=9.218Å, b=10.849Å, c=18.339Å, with unit cell volume is 2179.713(Å)3. Fluorescence spectra in methanolic solution reflect that intensity of emission for 1 is much higher compared to H2L and both the compounds exhibit good fluorescence properties. The complex 1 exhibits significant catalytic activities of biological relevance, viz. catechol oxidase. In methanol, it efficiently catalyzes the oxidation of 3,5-di-tert-butylcatechol (3,5-DTBC) to corresponding quinone via formation of a dinuclear species as [Zn2(L)(3,5-DTBC)]. Electron Paramagnetic Resonance (EPR) experiment suggests generation of radicals in the presence of 3,5-DTBC and it may be proposed that the radical pathway is probably responsible for conversion of 3,5-DTBC to 3,5-DTBQ promoted by complex of redox-innocent Zn(II) ion.

Crystal structure and magnetic properties of a tetranuclear carbonate-bridged CuII complex with a Schiff base compartmental ligand with the N2OS2 donor set

A carbonate-bridged tetranuclear CuII complex of the general formula [(Cu2L)2CO3]·2MeCN (L is triply deprotonated Schiff base condensation product of 1,3-diaminopropan-2-ol and 1-phenyl-3-methyl-4-formyl-5-mercaptopyrazole) has been obtained by the slow crystallization of dinuclear complex [(Cu2L)CCl3COO] from acetonitrile and studied by X-ray diffraction and low-temperature magnetic measurements.

Tautomerism of a compartmental Schiff base ligand and characterization of a new heterometallic CuII–DyIII complex — Synthesis, structure and magnetic properties

A crystal structure of a compartmental ligand N,N′-bis(2,3-dihydroxybenzylidene)-1,3-diaminopropane (H4L=C17H18N2O4) (1) containing N2O2-inner and O4-outer coordination sites and a characterization of its novel diphenoxo-bridged discrete dinuclear complex [CuDy(H2L)(MeOH)(NO3)3]·2MeOH (2) are reported. The Schiff base ligand 1 crystallizes in the orthorhombic P212121 space group with a molecule in a bent conformation. The compound at 100 and 293K displays the keto-enol tautomerism with the equilibrium in both temperatures shifted with a different degree towards the zwitterionic keto-amino form. The quantum chemical calculations showed preferences for enol-imino form in a gas phase and for keto-amine in solutions. The keto-amino tautomer is stabilized by intermolecular interactions. The complex 2 crystallizes in the triclinic P-1 space group as a dinuclear compound with CuIIDyIII core. The Dy(III) ion is nine-coordinated whereas the coordination number of Cu(II) is five. The temperature dependence of the magnetic susceptibility and the field-dependent magnetization indicated that the interaction between Cu(II) and Dy(III) metal centers in 2 is ferromagnetic.

Synthesis and Characterization of Compartmental Macrocyclic Binuclear Copper(II) Complex with Bidentate Perchlorato Ligand

Compartmental Schiff base ligand, Dinuclear complex, Bridging perchlorate anion, Macrocycliccopper(II) complex, Crystal structureIn recent years, there has been immense interest in study-ing binuclear metal complexes using macrocyclic compart-mental ligands derived from 2,6-diformyl-4-methylphenoland diamines.

Syntheses, structures, catecholase activity, spectroscopy and electrochemistry of a series of manganese(III) complexes: Role of auxiliary anionic ligand on catecholase activity

The work in this report presents the syntheses, characterization, catechol oxidase activity, electrochemistry and electrospray ionization mass spectroscopy (ESI-MS positive) of five mononuclear manganese(III) compounds [MnIIIL(OAc)(H2O)]·DMF (1), [MnIIIL(Cl)(H2O)]·2H2O (2), [MnIIIL(N3)(H2O)] (3), [MnIIIL(NCS)(H2O)] (4) and [MnIIIL(NCSe)(H2O)]·MeCN (5), derived from the Schiff base compartmental ligand N,N′-ethylenebis(3-ethoxysalicylaldimine) (H2L). All the five complexes are characterized by elemental analyses, FT-IR, UV–Vis spectra, molar conductance and single crystal X-ray structure determination. The structures of 1–5 show that these are mononuclear compounds in which the manganese(III) center occupies the N(imine)2O(phenoxo)2 compartment. In all structures, a dimer-of-mononuclear species is formed by bifurcated hydrogen bonding involving coordinated water molecule. The five mononuclear manganese(III) complexes 1–5 show catecholase activity with turnover (Kcat) numbers lying in the range 17.0–41.7h−1 (for 1–5) in DMF and 16.9–137.3h−1 (for 2–5) in MeCN. ESI-MS positive of 2–5 and their mixtures with 3,5-di-tert-butylcatechol have been recorded, revealing the existence of 3,5-di-tert-butylquinone containing species and a complex-substrate aggregate [MnIIIL(3,5-DTBCH)+H+]+. Cyclic voltammetric and square wave voltammetric studies of the compounds 1–5 reveal that these undergo quasireversible Mn(III)/Mn(II) redox couple with very close E½ values (from −200 to −213mV).

Homo- and Heterometal Complexes of Oxido–Metal Ions with a Triangular [V(V)O–MO–V(V)O] [M = V(IV) and Re(V)] Core: Reporting Mixed-Oxidation Oxido–Vanadium(V/IV/V) Compounds with Valence Trapped Structures

A new family of trinuclear homo- and heterometal complexes with a triangular [V(V)O-MO-V(V)O] (M = V(IV), 1 and 2; Re(V), 3] all-oxido-metal core have been synthesized following a single-pot protocol using compartmental Schiff-base ligands, N,N'-bis(3-hydroxysalicylidene)-diiminoalkanes/arene (H4L(1)-H4L(3)). The upper compartment of these ligands with N2O2 donor combination (Salen-type) contains either a V(IV) or a Re(V) center, while the lower compartment with O4 donor set accommodates two V(V) centers, stabilized by a terminal and a couple of bridging methoxido ligands. The compounds have been characterized by single-crystal X-ray diffraction analyses, which reveal octahedral geometry for all three metal centers in 1-3. Compound 1 crystallizes in a monoclinic space group P2(1)/c, while both 2 and 3 have more symmetric structures with orthorhombic space group Pnma that renders the vanadium(V) centers in these compounds exactly identical. In DMF solution, compound 1 displays an 8-line EPR at room temperature with <g> and <A> values of 1.972 and 86.61 × 10(-4) cm(-1), respectively. High-resolution X-ray photoelectron spectrum (XPS) of this compound shows a couple of bands at 515.14 and 522.14 eV due to vanadium 2p(3/2) and 2p(1/2) electrons in the oxidation states +5 and +4, respectively. All of these, together with bond valence sum (BVS) calculation, confirm the trapped-valence nature of mixed-oxidation in compounds 1 and 2. Electrochemically, compound 1 undergoes two one-electron oxidations at E(1/2) = 0.52 and 0.83 V vs Ag/AgCl reference. While the former is due to a metal-based V(IV/V) oxidation, the latter one at higher potential is most likely due to a ligand-based process involving one of the catecholate centers. A larger cavity size in the upper compartment of the ligand H4L(3) is spacious enough to accommodate Re(V) with larger size to generate a rare type of all-oxido heterotrimetallic compound (3) as established by X-ray crystallography.

New mononuclear CuII and tetranuclear CuII2–LaIII2 Schiff base complexes – Physicochemical properties

The new mononuclear inclusion compound [CuL⊂(H2O)] (1) and heterotetranuclear [Cu2La2(L)2(NO3)6(EtOH)2] (2) (L=C19H18N2O4Br2) complex, derived from the hexadentate Schiff base compartmental ligand N,N′-bis(5-bromo-3-methoxysalicylidene)propylene-1,3-diamine, have been synthesized and characterized by elemental analysis, XRF, FTIR, EPR and TG/DSC techniques. Their molecular structures have been confirmed by single crystal X-ray diffraction studies. Compound 1 crystallizes in the triclinic P1¯ space group with the Cu(II) ion occupying the N2O2 cavity and having a water molecule encapsulated by O–H⋯O hydrogen bonds in the O2O2 compartment. The tetranuclear complex 2 crystallizes in the monoclinic space group P21/c with only half of the molecule in the asymmetric unit. The inner N2O2 salen-type cavities are occupied by Cu(II) ions, whereas the La(III) ions are present in the open, larger O2O2 space of the Schiff base ligands. The two symmetrically independent heterodinuclear fragments of the molecule are bridged via nitrato ions, linking Cu(II) and La(III) ions. Magnetic studies for the complexes indicated a weak antiferromagnetic interaction between the copper(II) ions in the crystal lattice of 1 and in the tetranuclear unit of 2.

Diaquadinitratouranyl(VI) enforces the O(phenoxo)2O(methoxy)2 compartment of 3-methoxysalicylaldehyde-diamine ligands to interact with water molecules

This report presents the syntheses, characterization and crystal structures of [{CuIIL1}2·{(UVIO2)(NO3)2(H2O)2}] (1), [{CuIIL2}2·{(UVIO2)(NO3)2(H2O)2}]·2H2O (2) and [{CuIIL3}2·{(UVIO2)(NO3)2(H2O)2}]·2H2O (3) derived from three 3-methoxysalicylaldehyde-diamine Schiff base compartmental ligands H2L1, H2L2 and H2L3, in which the diimine moieties come from ethylenediamine, trans-1,2-diaminocyclohexane and ortho-phenylenediamine, respectively. Compounds 2 and 3 crystallize in triclinic crystal system having P1¯ space group, while compound 1 crystallizes in monoclinic symmetry with space group P21/c. The three structures are similar. The two coordinated water molecules in diaquadinitratouranyl(VI) occupy the two trans positions in the hexagonal basal plane of the hexagonal bipyramidal coordination environment. Each of these two water molecules interact, by forming bifurcated hydrogen bonds, with each of the two O(phenoxo)2O(methoxy)2 compartments resulting in the stabilization of the [1×2+1×1] trimetallic self-assemblies. The d–d spectra of 1–3 and the corresponding mononuclear copper(II) complexes [CuIIL1(H2O)]/[CuIIL2(H2O)]/[CuIIL3(H2O)] have been recorded. The previously proposed but little addressed correlation of d–d band position with the displacement of the copper(II) center from the least-squares basal plane has been highlighted, revealing the utilization of this correlation accompanied with the FT-IR data to judge the nature of water molecule in the mononuclear complexes. The unique features in the composition of 1–3 have been discussed.

Solvent‐dependent Switch of Magnesium Ions between Different Binding Sites in a Compartmental Schiff Base Ligand

AbstractThe coordination behavior of two Schiff base ligands, N,N′‐bis(3‐carboxysalicylidene)ethylenediamine (H2L1) and N,N′‐bis(3‐carboxysalicylidene)propylenediamine (H2L2), towards magnesium ions is reported. The ligands show different binding site selectivity for Mg2+ depending on the solvent. In complexes isolated from aqueous or methanolic solutions the metal ion resides in the outer O2O2 compartment. The X‐ray analysis of the complex of H2L1 showed the complex to be dimeric with magnesium being coordinated by two phenolate and two carboxylate oxygens, a bridging phenolate oxygen, and a water ligand. In aprotic solvents like dimethylsulfoxide (DMSO) and dimethylformamide (DMF) magnesium migrates to the inner N2O2 binding site. In DMSO solution containing small amounts of water, both isomers co‐exist. A similar solvent‐dependent site selectivity is not observed for zinc ions.

More surprising differences between two closely similar compartmental ligand families and another dinuclear synthon to stabilize dinuclear–mononuclear cocrystals

This paper presents syntheses, characterization, crystal structures and magnetic properties of two diphenoxo-bridged heterodinuclear CuIIMnII/CuIIFeII compounds [CuIIL1MnII(H2O)3](ClO4)2 (1) and [CuIIL1FeII(H2O)3](ClO4)2 (2) and two tetranuclear CuII3MnII/CuII3FeII compounds [{CuIIL2MnII(H2O)(MeOH)2}(CuIIL2)2](ClO4)2·MeOH (3) and [{CuIIL2FeII(H2O)(MeOH)2}(CuIIL2)2](ClO4)2·MeOH (4) derived from two 3-methoxysalicylaldehyde-diamine Schiff base compartmental ligands H2L1 and H2L2, in which the diamine counterpart comes from 1,3-diaminopropane and o-phenylenediamine, respectively. The two compounds 1 and 2 crystallize in the same space group (monoclinic P21/n) with practically identical unit cell parameters and are isomorphous. Similarly, the two compounds 3 and 4 crystallize in the same space group (monoclinic P21/c) with practically identical unit cell parameters and are isomorphous. The tetranuclear [{CuIIL2MII(H2O)(MeOH)2}(CuIIL2)2]2+ dication in 3 (M = Mn) and 4 (M = Fe) is a self-assembly of one diphenoxo-bridged dinuclear [CuIIL2MII(H2O)(MeOH)2]2+ dication and two mononuclear [CuIIL2] units. One mononuclear unit is self-assembled with the dinuclear unit by four bifurcated water⋯phenoxo/methoxy (O–H⋯O) hydrogen bonds and three π⋯π stacking interactions, while the second mononuclear unit is interlinked with the dinuclear unit by one methanol⋯phenoxo (O–H⋯O) hydrogen bond only. Clearly, compounds 3 and 4 are [2 × 1 + 1 × 2] cocrystals of one dinuclear and two mononuclear units. Variable-temperature magnetic susceptibility measurements of all the four compounds have been carried out, revealing moderate antiferromagnetic interaction between the copper(II) and manganese(II)/iron(II) in the dinuclear cores with J values (H = −2JS1S2) −29.1, −36.9, −15.9 and −20.2 cm−1, respectively. The magnetic properties are in line with those of previous related examples. Unique features in the structures of 1–4 have been discussed.

Metal complex analogues of crown ethers as the preorganized motif to stabilize aquated proton in solid state

The work in this report presents the syntheses, characterization and crystal structures of [{CuIILop}2(H5O2)](ClO4) (1), [{CuIILhex}2(H5O2)](ClO4) (2) and [{CuIILen}2(H5O2)](ClO4) (3) derived from three 3-ethoxysalicylaldehyde-diamine Schiff base compartmental ligands H2Lop, H2Lhex and H2Len, in which the diimine moieties come from ortho-phenylenediamine, trans-1,2-diaminocyclohexane and ethylenediamine, respectively. Compounds 1 and 2 crystallize in triclinic crystal system having P space group, while the crystal system and space group of compound 3 is monoclinic P21/c. In the [{CuIILop/hex/en}2(H5O2)]+ cation in 1–3, the two OH2 sites of the aquated proton, H5O2+, interact with two O(phenoxo)2O(ethoxy)2 compartments of the two [CuIILop/hex/en] moieties by forming bifurcated hydrogen bonds and thus [{CuIILop/hex/en}2(H5O2)]+ may be considered as a supramolecular dimer of two mononuclear moieties, self-assembled by H5O2+ as the tecton. On the basis of the extent of the difference in the two O–H distances involving the central hydrogen atom, H5O2+ moieties in 1–3 may be considered as H2O+–H⋯OH2 (in 1) or as the resonance hybrid of H2O+–H⋯OH2 and [H2O⋯H⋯OH2]+ (in 2 and 3). A unique aspect in the composition of 1–3 in terms of the interaction of metal complexes with an aquated proton has been discussed.