Utilizing deprotonated forms of pyridine-/pyrazine-2-carboxamide ligands, the synthesis and structural characterization of hetero-bimetallic complexes [NiII(Lpy)3CoIICl]6H2O (1), [NiII(Lpy)3ZnIICl]xH2O (2), [CoII(Lpz)3ZnIICl]H2O (3), [CoIII(Lpz)3ZnIICl](PF6)(C2H5)2OCH3CNH2O (4), [NiII(Lpz)3CoIICl]H2O (5), and [NiII(Lpz)3ZnIICl]H2O (6) have been achieved. Structural studies reveal that six-coordinate Co(ii), Co(iii), and Ni(ii) are supported by three bidentate Lpy(-) or Lpz(-) ligands utilizing deprotonated pyridine-2-carboxamide or pyrazine-2-carboxamide providing three pyridine/pyrazine N and three amidate N and such a situation in turn places three pyridine nitrogens of the 4-methyl-2-aminopyridine units to act as a tridentate N3 facial-capping ligand to hold other bivalent metal ions Co(ii) or Zn(ii). The fourth coordination site around the distorted tetrahedral bivalent metal ion is completed by a chloride ion originating from the Co(ii) or Zn(ii) starting material. A facile CoIII/CoII redox process in 3 and 4 and NiIII/NiII redox process in 1, 2, 5, and 6 have been observed. It has been demonstrated that by changing the donor site of pyridine N to pyrazine N, the oxidation state of the metal ion in both Co(ii) and Co(iii) could be readily accessed in the synthesis of 3 and 4, attesting that a pyrazine stabilizes the lower oxidation state of a metal ion better than a pyridine. Solid-state magnetic susceptibility measurements on 1 and 5 in the range of 2-300 K revealed weak antiferromagnetic coupling between the six-coordinate Ni(ii) (S = 1) and four-coordinate Co(ii) (S = 3/2) centers.

Using an unsymmetrical facially-capping tridentate N-donor ligand, N-methyl-N-(2-pyridylmethyl)-N-(2-pyridylethyl)amine (L1), we reported the synthesis and properties of [(L1)2MnIII2(μ–O)(μ–O2CMe)2]X2.H2O (X = PF6– 1a•H2O, X = ClO4– 1b•H2O; Mahapatra et al. Inorg. Chem. 1994, 33, 1579–1580 and Lal et al. Inorg. Chem. 1998, 37, 2373–2382), [(L1)2MnIII,IV2(μ–O)2(μ–O2CMe)](ClO4)2•H2O 2a•H2O (Mahapatra et al. J. Chem. Soc., Dalton Trans. 1993, 317–320; structurally characterized as [(L1)2MnIII,IV2(μ–O)2(μ–O2CMe)](BF4)2•2MeCN (2b•2MeCN) and [(L1)2MnIV2(μ–O)2(μ–O2CMe)](ClO4)3•2H2O (3•2H2O): Lal et al. Inorg. Chem. 1998, 37, 2373–2382). Using a symmetrical facially-capping tridentate N-donor ligand, N-methyl-N,N-bis(2-pyridylmethyl)amine (L2), the syntheses and physicochemical properties of [(L2)2MnIII2(μ–O)(μ–O2CMe)2](ClO4)2•CH2Cl2 (4•CH2Cl2), [(L2)2MnIII/IV2(μ–O)2(μ–O2CMe)](ClO4)2 (5) and [(L2)2MnIV2(μ–O)2(μ–O2CMe)](ClO4)3•2H2O (6•2H2O) are described. Crystal structures of 1b•H2O, 3•3MeCN, 4•CH2Cl2, 5, and density function theory (DFT)-calculated structure of 6 are presented here. While 4•CH2Cl2 and 6•2H2O are EPR-silent, 5 has S = 1/2 ground-state and its X-band EPR spectrum at 120 K exhibits 16-line spectrum at g 2. Variable-temperature magnetic susceptibility measurements revealed ferromagnetic coupling of spins in 4•CH2Cl2 and strongly antiferromagnetic coupling in 5 and 6•2H2O [H = –JS1•S2; J = +29 cm–1 (4•CH2Cl2); J = –315 cm–1 (5); –300 cm–1 (6•2H2O)]. With the dimers MnIII2, MnIII,IV2 and MnIV2 of L1 and L2, and closely similar reported complexes of L3, systematic magneto-structural studies have been attempted and for the first time useful linear correlations of this class of Mn-dimers have been obtained. When examined by cyclic voltammetry (V vs. SCE), 4•CH2Cl2 and 6•2H2O exhibit MnIV2/MnIII,IV2 redox process at 0.92 V, which are one-electron oxidative and one-electron reductive, respectively. Complex 4•CH2Cl2 in MeCN exhibits two anodic responses due to [(L2)2MnIII(–O)(–O2CMe)2MnIV]3+/[(L2)2MnIII(–O)(–O2CMe)2MnIII]2+ (E1/2 = 1.07 V) and [(L2)2MnIV(–O)2(–O2CMe)MnIV]3+/[(L2)2MnIV(–O)2(–O2CMe)MnIII]2+ (E1/2 = 0.92 V) redox processes (electron transfer followed by chemical reaction and again electron transfer (ECE) mechanism). When reacted (1:1) with (IV,IV) dimer 6•2H2O (S = 0) and the phenolic substrate 2,4,6-tri-tert-butylphenol, 16-line EPR signal was observed due to the formation of a MnIII,IV2 dimer (S = 1/2), along with a sharp signal at g = 2.004 due to 2,4,6-tri-tert-butylphenoxyl radical. Reaction of 6•2H2O and 2,4-di-tert-butylphenol, afforded phenoxyl radical-derived C–C coupled organic product and from such a reaction mixture a four-electron reduced product [MnII(L2)2](ClO4)2•MeOH (7•MeOH) has been isolated and structurally chara

A family of five 1D Re IV Ln III [Ln III = Dy, Tb, Gd] complexes based on derivatives of (3,4- and 3,5-)pyridinedicarboxylic acid has been prepared and characterised. The Re IV Dy III -based family members exhibit field-induced slow magnetic relaxation.

The design and synthesis of molecule-based multifunctional magnetic materials (MMMs) with desired chemical (e.g., host-guest, catalytic, acid-base, or redox) and physical (e.g., optical, magnetothermal, proton, or electron conducting) properties, in addition to magnetism, constitute a major goal in coordination chemistry. A deep knowledge of the metal-ligand self-assembly and metalloligand design approaches is essential for achieving the synergy that elevates classical molecular magnets and nanomagnets into the realm of MMMs. This review chronicles the journey of the versatile oxalato-type ligand family—including oxalate (ox), oxamate (oxa), oxamidate (oxm), dithiooxalate (dto), and tetrathiooxalate (tto)—in building homo- and heterometallic polynuclear complexes (PCs) and coordination polymers (CPs). These systems incorporate paramagnetic transition (nd, n = 3–5) and rare-earth (4f, 5f) metal ions, alongside diamagnetic alkaline or alkaline-earth ones, to construct MMMs ranging from discrete metal-organic clusters (MOCs) to extended metal-organic frameworks (MOFs). Ultimately, this review demonstrates how the foundational principles of magnetochemistry, established with this versatile ligand family, are now providing a robust blueprint for tackling the great challenges of the third millennium: designing advanced materials for quantum information processing, sustainable catalysis, selective molecular biosensing, diagnostic imaging, cryomagnetic refrigeration, water remediation, and chemical decontamination.

An isostructural series of neutral cyano-bridged tetranuclear iron(iii)-lanthanide(iii) complexes of general formula {[Fe(htpzb)(CN)(mu-CN)2]2[Ln(dmbpy)(NO3)2(H2O)]2}2CH3CN2H2O [Ln = Gd (1), Tb (2), Dy (3), Ho (4), and Er (5); htpzb = hydrotris(pyrazolyl)borate and dmbpy = 4,4 '-dimethyl-2,2 '-bipyridine] was synthesized and structurally and magnetically characterized. Single-crystal X-ray analysis of 1-5 revealed the formation of neutral cyano-bridged {FeIII2LnIII2} complexes (Ln = Gd, Tb, Dy, Ho, and Er) of square-like topology that crystallize in the triclinic P1 space group. Solid-state direct-current magnetic susceptibility analysis evidenced weak intramolecular antiferromagnetic FeIII-LnIII interactions in 1 (Ln = Gd) together with large local magnetic anisotropies from the LnIII ion in 2-5 (Ln = Tb, Dy, Ho, and Er). Frequency-dependent alternating current magnetic susceptibility signals occurred for 1-5 under an applied dc magnetic field of H = 1.0 (1) or 0.5 T (2-5), indicating field-induced slow magnetic relaxation effects typical of single-molecule magnets. Depending on the non-Kramer (Tb, Ho) or Kramer (Gd, Dy, Er) nature of the LnIII ion, a single magnetic relaxation process via Orbach or Raman mechanism (2 and 4) or a multiple magnetic relaxation process that combines Orbach or Raman plus quantum tunneling of magnetization and/or direct (1, 3, and 5) mechanisms occurred along this series. 1-5 showed large magnetocaloric effects with a high to moderate maximum value of the magnetic entropy change at optimum working temperatures just above He liquefaction [-Delta Smax = 16.51 (1), 5.42 (2), 6.02 (3), 4.56 (4), and 5.86 J kg-1 K-1 (5) for H = 5 T at Topt = Tmax = 2 (1), 4 (2, 3 and 5), and 6 K (4)], as well as a high to moderate magnetocaloric index at rather low optimum working fields [MCI = 6.4 (1), 3.3 (2), 4.7 (3), 0.9 (4), and 3.6 J kg-1 K-1 T-1 (5) for Hopt = Hmax = 1.0 (1), 0.6 (2), 0.4 (3), 0.8 (4), and 0.6 T (5) at T = 2 K].

A new mononuclear gadolinium(III) complex with the antenna-type 3,6-di(2-pyridyl)pyridazine ligand (dppn) has been synthesized and structurally, spectroscopically, and magnetically characterized. It exhibits visible ligand-centered fluorescence when excited with UV light, together with field-induced slow magnetic relaxation and large magnetocaloric effects at low temperatures (-Delta Smax = 26.0 J Kg-1 K-1 at T = 2 K and H = 7 T). The magnetic relaxation mechanism is dominated by a Raman process mediated by optical phonons (n = 3.06), instead of an Orbach process through a magnetic anisotropy barrier, as expected from an almost isolated, isotropic GdIII ion with very weak intermolecular interactions (theta =-0.059 K).

Square-like cyano-bridged {Ln 2 III Fe 2 III } field induced SMMs and magnetic coolers operating just above the helium liquefaction temperature have been reported.

The design and the synthesis of molecule-based crystalline salts made up of simple cationic and/or anionic building blocks with multiple, occasionally stimulus-responsive, chemical (host–guest, catalytic, acid–base, or redox) and physical (optical, magnetic, or conducting) properties constitute two major goals in inorganic, organic, organometallic, and coordination chemistries. A deep knowledge of the basic features of molecular and supramolecular interactions that occur in the solid state is needed to progress along these tasks to obtain new advanced multifunctional materials. Inspired by the outstanding research of several groups on magnetic molecular salts from the mid-1970s to the present day, this review offers a personal portrayal of the history of molecular magnetism and molecular electronics and its current evolution toward molecular spintronics and quantum computing. We focus on the well-known families of molecular salts based on paramagnetic tetrathiafulvalenium/tetraselenafulvalenium or tetracyanoethenide/tetracyanoquinodimethanide organic radicals, cyclopentadienide/cyclooctatetraenide metallocenium complexes, and polyhalide/polycyanide, porphyrin/phthalocyanine, oxalate/dithiooxalate, or dithiolene/dithiolate metal complexes with first-, second-, or third-row transition metal (nd, n = 3–5) and lanthanide (4f) ions. This old but evergreen class of magnetic molecular salts provides illustrative “textbook” examples of advanced multifunctional materials such as molecular magnets and conductors, molecular magnetic conductors, molecular nanomagnets, and molecular quantum bits with potential nanotechnological applications in quantum information storage and processing.

Anaerobic reaction between solution‐generated copper(I) species ‘[(L 3 )‐Cu I (MeCN)] + ’ (L 3 is an unsymmetrical tridentate ligand; methyl[2‐(2‐pyridyl)ethyl](2‐pyridylmethyl)amine) and dry O 2 in CH 2 Cl 2 , after usual workup under a dinitrogen atmosphere, afforded a green microcrystalline solid. Recrystallization of this air‐sensitive solid from MeCN/diethyl ether led to isolation of [{(L 3 )‐Cu II (μ‐OH)} 2 ](ClO 4 ) 2 •MeCN ( 1 •MeCN). Structural analysis of 1 •MeCN reveals a μ‐dihydroxido‐bridged dicopper(II) complex with a Cu⋯Cu separation of 2.9088(12) Å. The intramolecular magnetic coupling between the Cu(II) ( S = 1/2) centers is weakly antiferromagnetic ( J = −0.62 cm −1 ; g = 2.07). Reactions between 1 •MeCN and ethyl acetate (EtOAc) or ethyl benzoate (EtOBz) in DMF at ≈60 °C led to hydrolysis of carboxy esters and afforded isolation of mononuclear acetate‐ and benzoate‐bound complexes [(L 3 )‐Cu II (OAc)(OClO 3 )] ( 2 ) and [(L 3 )‐Cu II (OBz)(H 2 O)](ClO 4 ) ( 3 ), respectively. A rationale, involving monomer–dimer equilibrium, has been provided for the observed hydrolysis of carboxy esters, where controlled isotopic labeling experiments using 18 O 2 support involvement of the μ‐hydroxido group of 1 •MeCN in carboxylate formation during ester hydrolysis. A similar reaction between 1 •MeCN and bis(4‐nitrophenyl)phosphoric acid (Hbnpp) led to isolation of a 1D‐coordination polymer {[(L 3 )‐Cu II (bnpp)](ClO 4 )} n ( 4 ). Complexes 2 – 4 have also been structurally characterized.

Detecting biogenic amines (BAs) is a topic of particular interest for future technological applications of metal-organic frameworks (MOFs) in food quality control. Herein, we demonstrate that integrating lanthanide single-ion magnets (SIMs) into MOFs offers a convenient route for developing a new class of luminescent spin quantum sensors for BA sensing, termed Ln SIM-MOFs. This study focuses on the well-known family of lanthanide(III) sesquioxalate hydrates of general formula {[LnIII2(ox)3(H2O)6]·xH2O}n, which feature a 2D hexagonal layer structure. Upon selective adsorption of methylamine over di- or trimethylamine vapors, these compounds exhibit either a partial quenching of the luminescence [Ln = Eu 1a (x = 3) and Tb 2a (x = 3)] or a dramatic change of the spin dynamics from a slower to a faster relaxing phase [Ln = Er 3a (x = 2.5)]. The dual luminescent and magnetic vaposwitching behavior observed in this series of dynamic Ln SIM-MOFs offers new design principles to obtain multifunctional and multiresponsive molecular materials for the chemical sensing of volatile organic compounds (VOCs), resulting from industrial procedures or food degradation.

The reaction in reagent grade acetone of copper(II) nitrate hexahydrate, 2,2′-bipyrimidine (bpm) and potassium iodide in a 1:2:2 molar ratio afforded three different products: an unreduced Cu(II) species, a fully reduced Cu(I) species and a mixed-valent Cu(II)/Cu(I) species. Of these, only the unreduced Cu(II) complex of formula [CuII(bpm)3](I3)(I) (1) could be structurally characterized, the other two products being initially only isolated as amorphous powders. X-ray quality, beautifully shaped, quasi-black prismatic crystals of compound 2, namely {[CuI(I3)CuII(I)(bpm)2](I3)}n, and brick-reddish parallelepipeds of compound 3, namely {[CuI2 (μ-I)2(bpm)]}n, were successively obtained through the slow diffusion in H-shaped tubes of aqueous solutions of the three reagents, after extensive optimization of the crystallization conditions. Compound 1 consists of a rare tris(2,2′-bipyrimidine)copper(II) monomeric dication, charge balanced by both iodide and triiodide anions. Compound 3, whose structure as well as optical and photocatalytic properties were recently disclosed, consists of a regular alternating μ-bpm/di-μ-iodide copper(I) chain. Finally, compound 2 consists of a rare, regular alternating mixed-valent Cu(II)-Cu(I) μ-bpm copper chain, showing unusual similarities in the metal coordination environment. The magnetic properties of compound 2 remarkably reveal a very weak antiferromagnetic coupling between the paramagnetic Cu(II) ions which are well separated both intra- and inter-chain.

The copper(II) complexes {Na4(H2O)8[Cu2(acriba)2(H2O)2]}n·4nH2O (1) and (Bu4N)4[Cu2(acriba)2]·5H2O (2) [H4acriba = N,N'-3,6-acridinebis(oxamic acid) and Bu4N+ = tetra-n-butylammonium cation] have been synthesized and characterized. Their crystal structures revealed the occurrence of [Cu2(acriba)2(H2O)2]4- (1) and [Cu2(acriba)2]4- (2) units of the [3,3] metallacyclophane-type which are built by two acridine linkers connected by two N-Cu-N bonds. The electroneutrality in 1 is achieved by their coordination to hydrated sodium(I) cations to afford a heterobimetallic sheet-like polymer, whereas that in 2 is ensured by bulky organic Bu4N+ cations to yield well-separated discrete dicopper(II) complexes. The spectrophotometric study of the catalytic activity of 1 and the related complex [Na6Cu2(mpyba)2Cl2(H2O)8]·7H2O (3) [H4mpyba = N,N'-2,6-pyridinebis(oxamic acid)] towards the oxidation of phenolic derivatives in aqueous solution showed a remarkable catalytic performance only for the hydroquinone with a better catalytic role in the case of 1. This superior catalytic behavior may be explained by the higher Lewis acidity of the Cu(II) ions derived from the inherent electronic delocalization of the extended aromatic acridine fragment compared to the pyridine one. The magnetic properties of 1 and 2 show weak intramolecular ferromagnetic interactions within their metallacyclophane units [J = +1.83 (1) and +1.72 cm-1 (2); H = -JSCu1·SCu2 where SCu1 = SCu2 = 1/2], their nature and magnitude being substantiated by theoretical calculations. These two examples illustrate the ability of the acridine moieties to mediate ferromagnetic interactions between copper(II) ions through the very long -Namidate-C-C-C-N-C-C-C-Namidate- exchange pathway in the context of the spin polarization mechanism.

Three new trinuclear copper(II) complexes [Cu-3(II)(L-2)(4)(2-picolinate)(2)(OClO3)(2)](ClO4)(2)2CH(3)COCH(3)2CH(3)OH (1), [Cu-3(L-2)(4)(2-picolinate)(2)(CH3OH)(2)(OClO3)(2)](ClO4)(2) (1a) and [Cu-3(II)(L-2)(4)(2,6-dipicolinate)(2)](ClO4)(2)6CH(3)OH2H(2)O (2) (L-2 = 1-benzyl-[3-(2 '-pyridyl)]pyrazole; 2-picolinate = 2-pyridinecarboxylate ion and 2,6-dipicolinate = 2,6-pyridinedicarboxylate ion) have been synthesized and structurally characterized. Complexes 1 and 1a differ only in the terminal Cu(II) coordination; 1 has five- (distorted trigonal-bypyramidal) and 1a has six- (distorted octahedral with additional CH3OH coordination), due to slightly differing crystallization conditions. In 1 and 1a, the central Cu(II) ion is six-coordinate in which the four equatorial positions (N2O2) are occupied by two 2-picolinate ions and two apical positions are occupied by two perchlorate ions. In 2 the central Cu(II) ion is coordinated by two tridentate 2,6-dipicolinate ions. Each terminal Cu(II) ions in 1 and 2 are coordinated by two L-2 ligands and by an carboxylate O from central Cu(II) bridged by 2-picolinate (mu(2)-1,3) in 1 and 1a or 2,6-dipicolinate (mu(2)-1,1) in 2 both in the syn-anti mode. The three Cu(II) ions in 1, 1a and 2 are in a grossly linear arrangement. Susceptibility measurements (2-300 K) on 1 and 2 reveal weak ferromagnetic coupling J = 4.01 cm(-1) and J = 8.22 cm(-1), respectively, leading to a quartet ground state.

Reactions of LXYL17 or LXYL18 (LXYL17 = alpha,alpha '-bis[((1-methyl-2-benzimidazolyl)methyl)-N-(6-methyl-2-pyridylmethyl)-amino]-m-xylene; LXYL18 = alpha,alpha '-bis[((1-methyl-2-benzimi-dazolyl)-methyl)-N-(2-pyridylethyl)-amino]-m-xylene) with [Cu(MeCN)4](ClO4) in CH2Cl2 at 298 K, subsequent exposure to dioxygen, and work-up from MeCN-MeOH, led to [CuII 2(LXYL17)(mu-OMe)2](ClO4)2 center dot 05H2O (1) and [CuII 2(L XYL18)(mu-OMe)2](ClO4)2 center dot 0.5MeCN (2). Structural characterization revealed their bis(methoxido)-bridged binuclear copper(II) structure. The well-known ring-hydroxylation of the xylyl-spacer has not been observed here. In both 1 and 2, each copper(II) center is terminally coordinated by a common N-methyl-benzimidazolyl nitrogen and a tertiary amine nitrogen; in 1 , an additional terminal coordination is provided by a 6-methyl-2-pyridylmethyl nitrogen, generating a five-membered and in 2 it is by a 2-pyridylethyl nitrogen, generating a six-membered chelate ring. The binuclear copper(II) complexes have Cu & mldr;Cu separation of 3.0239(16) & Aring; (1) and 3.0022(17) & Aring; (2). The geometry around the two Cu(II) centers is almost ideal square-pyramidal in 1 (tau values: 0.05 and 0.015) and slightly distorted in 2 (tau values: 0.23 and 0.243). Magnetic susceptibility measurements (100-300 K) on 1 and 2 reveal strong antiferromagnetic coupling J = -916(10) cm-1 for 1 and J = -820(10) cm-1 for 2. The differential magnetic coupling is fine-tuned by structural differences exerted by two subtly different non-Schiff base m-xylyl-based terminal N3 ligands.

In this work, we describe the synthesis, crystal structures and magnetic properties of four air-stable mononuclear lanthanide(III) complexes with the N-(2,4,6-trimethylphenyl)oxamate (Htmpa) of formula: n-Bu4N[Nd(Htmpa)4(H2O)]·4H2O (1), n-Bu4N[Gd(Htmpa)4(H2O)]·3DMSO·2H2O (2), n-Bu4N[Tb(Htmpa)4(H2O)]·3DMSO·1H2O (3) and n-Bu4N[Dy(Htmpa)4(H2O)]·3DMSO·2H2O (4) (n-Bu4N+ = n-tetrabutylammonium; DMSO = dimethylsulfoxide). Their crystal structures reveal the occurrence of calixarene-type monoanionic species containing all-cis-disposed Htmpa ligands and one water molecule coordinated with the respective LnIII ion (Ln = Nd, Gd, Tb and Dy), featuring a nine-coordinated environment with muffin (MFF-9) (1) or spherical-capped square antiprism (CSAPR-9) (2–4) geometry. The major difference between their crystal structures is related to the nature of crystallization solvent molecules, either water (1) or both DMSO and water (2–4). The intermolecular hydrogen bonds among the self-complementary Htmpa ligands in all four compounds mediated a 2 D supramolecular network in the solid state. Direct-current (dc) magnetic properties for 1–4 show typical behavior for the ground state terms of the LnIII ions [4I9/2 (Nd); 8S7/2(Gd), 7F6 (Tb), 6H15/2 (Dy)]. Alternating-current (ac) magnetic measurements reveal the presence of slow magnetic relaxation without the presence of a dc field only for 4. In contrast, field-induced slow magnetic relaxation behavior was found in complexes 1, 2 and 3.

A unique series of spin-crossover cobalt( ii )-pyridine-2,6-dimine molecular nanomagnets as prototypes of molecular spin quantum transitors and capacitors exhibiting a dual metal- and ligand-centred multielectron redox behaviour is reported.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

A 3D coordination polymer of Tb( iii ) of formula [Tb(bttb) 0.5 (2,5-pzdc) 0.5 ] n , where two polycarboxylate ligands act as linkers, exhibits a maximum relative sensitivity of 0.76% K −1 at 295 K.

Coexistence of tunable spin-crossover and field-dependent single-molecule magnet behaviours in cobalt( ii )-pyridine-2,6-diiminephenyl complexes.