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Two complexes {[GdCu 5 (GlyHA) 5 (H 2 O) 7 Cr(C 2 O 4 ) 3 ]·11.02H 2 O} n (1) and {{[GdCu 5 (GlyHA) 5 (H 2 O) 6 ]μ 2 -[Cu(C 2 O 4 ) 2 (H 2 O)]} 2 μ 4 -[Cu(C 2 O 4 ) 2 ]·15.8H 2 O} n (2), were obtained as outcomes of the reactions between the cationic hexanuclear {GdCu 5 (GlyHA) 5 } 3+ 15-metallacrown-5 complex (where GlyHA 2- = glycinehydroxamate) and the anionic oxalate complexes K 3 [Cr(C 2 O 4 ) 3 ] or K 2 [Cu(C 2 O 4 ) 2 ]. Both 1 and 2 possess polymeric 1D-chain structures according to X-ray structural analysis. As a consequence of the geometric orientations of the donor atoms in the oxalates from [Cr(C 2 O 4 ) 3 ] 3- , the Cu 5 mean planes of neighboring 15-metallacrown-5 units {GdCu 5 (GlyHA) 5 } 3+ are angled at 75.5° to each other, which leads to formation of a zig-zag motif in the 1D-chains of complex 1. The centrosymmetric complex 2 contains two structurally different bis(oxalato)cuprate anions μ 2 -[Cu(C 2 O 4 ) 2 (H 2 O)] 2- , for one of which, coordination to two adjacent {GdCu 5 (GlyHA) 5 } 3+ units leads to formation of linear 1D-chains in 2, while the second type, μ 4 -[Cu(C 2 O 4 ) 2 ] 2- , is coordinated to four {GdCu 5 (GlyHA) 5 } 3+ units, causing the cross-linking of single 1D-chains into a double-chain 1D coordination polymer. Studies of χ M T vs. T data for 1 and 2 in a 2-300 K temperature range revealed the presence of both ferromagnetic and antiferromagnetic interactions amongst paramagnetic centres. The experimental χ M T vs. T data for 1 were fitted using a model which takes into account exchange interactions between adjacent copper(II) ions, the Gd-Cu exchange interactions within {GdCu 5 (GlyHA) 5 } 3+ units and additionally Gd-Cr exchange interactions. Fitting of the χ M T vs. T data for 2 was not possible, since coordination of μ 4 -[Cu(C 2 O 4 ) 2 ] 2- to {GdCu 5 (GlyHA) 5 } 3+ led to the non-equivalence of several Cu-Cu exchange interactions within the metallacrown units and hence a superfluity of fittable parameters. Complexes 1 and 2 are the first examples of 15-metallacrown-5 complexes demonstrating a magnetocaloric effect (-Δ S M at 13 T reaches 24.26 J K -1 kg -1 at 5 K and 19.14 J K -1 kg -1 at 4 K for 1 and 2, respectively).

An in situ hydrolysis of the P-Cl bonds of the carbophosphazene [{NC(NMe 2 )} 2 {NPCl 2 }] (L PCl 2 ) in the presence of hydrated lanthanide(III) nitrates in a dichloromethane and methanol (2 : 1) solvent mixture afforded a series of novel 1D coordination polymers: [{Ln(L HPO 2 ) 3 (NO 3 ) 2 (CH 3 OH)(H 2 O)} (Cl)] n {where Ln(III) = Gd (1), Tb (2), Dy (3), or Er (4) and L HPO 2 is the hydrolyzed carbophosphazene (L PCl 2 ) ligand}. X-ray crystallographic analysis revealed that complexes 1-4 are isostructural and crystallized in the monoclinic crystal system having P 2 1 / c space group. The coordination polymers are formed because of the involvement of the geminal P(O)(OH) moieties of the carbophosphazene ligand. Each lanthanide(III) ion is 9-coordinate (9O) in a distorted muffin geometry. Magnetic measurements revealed that both Dy III and Er III analogues exhibit field-induced single-molecule magnet (SMM) behavior at 0.8 kOe and 2.2 k Oe, respectively. At such dc fields, the dynamic magnetic susceptibility displays complex behavior with a triple magnetic relaxation contribution for 3, while two contributions were identified for 4. The observed static and dynamic magnetic behavior for complexes 1-4 were further rationalized with the aid of BS-DFT and CASSCF/SO-RASSI/SINGLE_ANISO calculations.

The association of lanthanide ions and paracyclophane derivatives has been very scarcely reported in the literature. In this study, elaboration of five coordination lanthanide complexes involving the 1,4(1,4)-dibenzenacyclohexaphane-1 2 ,4 3 -diylbis(diphenylphosphine oxide) ligand ( L ) was achieved with the determination of single-crystal X-ray diffraction structures of four mononuclear complexes of formula [Ln(hfac) 3 ( L )] (hfac- = 1,1,1,5,5,5-hexafluoroacetylacetonate) (Ln = Dy(III) (1-Dy) and Yb(III) (2-Yb)) and [Ln(tta) 3 ( L )] (tta - = 2-tenoyl-trifluoroacetylacetonate) (Ln = Dy(III) (3-Dy) and Yb(III) (4-Yb)) and one dinuclear complex [Na(Dy 2 (hfac) 6 ( L ) 2 )](BArF) (BArF - = tetrakis[3,5-bis(trifluoromethyl)phenyl]borate) (5-Dy). The compounds were characterized using elemental analysis, IR spectroscopy, DC and AC magnetic measurements and photophysical investigations. L is an efficient organic chromophore for the sensitization of both visible Dy(III) (1-Dy) and near-infrared Yb(III) (2-Yb and 4-Yb) luminescence. The combination of excitation and emission spectra allowed the determination of the crystal field spitting of both the 2 F 7/2 ground state and 2 F 5/2 excited state for 2-Yb and 4-Yb. Moreover, 3-Dy and the two Yb(III) derivatives displayed field-induced single-molecule magnet (SMM) behaviour with slow magnetic relaxation occurring through the Raman process only for 2-Yb and 4-Yb, whereas a combination of Orbach and Raman processes was identified for 3-Dy.

We report three Co II -based complexes with the general formula [Co II (L)(X) 2 ] by changing the halide/pseudo-halide ions [X = NCSe (1SeCN); Cl (2Cl) and Br (3Br)]. The obtained τ 5 and CShM values confirm a distorted square pyramidal geometry around the Co II ion in all these complexes. In these three complexes, the central Co II ion is situated above the basal plane of the square pyramidal geometry. The extent of distortion from the ideal SPY-5 geometry differs upon changing the coordinating halide/pseudo-halide ion in these complexes. This essentially results in the alteration of the anisotropic parameter D and hence impacts the magnetic properties in these complexes. This phenomenon has been corroborated with the aid of theoretical investigations. All these complexes display field-induced SIM behaviour with magnetic relaxation occurring through a combination of processes depending on the applied dc magnetic field values and dilution.

In this work, a new family of binuclear Ni II -Ln III complexes with the formula [NiLn(L) 2 (NO 3 ) 3 ]·0.5H 2 O (Ln = Gd, 1; Tb, 2; Dy, 3; Ho, 4; Er, 5; Yb, 6; Y, 7) was synthesized using a thioether group-bearing Schiff base. Due to the strict hard/soft dichotomy between the 4f and 3d metal ions, selective coordination of Ni II and 4f metal ions was achieved with the adjacent soft ONS and hard OO binding pockets of the ligand. All the complexes 1-7 exhibit a Ni II centre in a distorted pseudo-octahedral geometry with the Ln III centres in distorted bicapped square-antiprism geometry. The huge distortion around the Ni II centres is triggered for the accommodation of larger lanthanoids to the adjacent OO coordination site, and this forces the Ni II centres to have a tridentate coordination from the ONS, as intermediate between meridional and facial binding. Field-induced single-molecule magnetic behaviour was observed for heterodinuclear complexes involving Kramers lanthanide ions (Ln III = Dy, Er and Yb), with magnetic relaxation occurring through an Orbach process only for 5. DFT calculations using various functionals (BP86, B3LYP, PBE0, TPSSh, PWPB95, R 2 SCAN) were applied to calculate the isotropic exchange, showing good agreement with the experiment ( J Gd-Ni = +1.78 cm -1 ). CASSCF calculations for Ni II and Ln III ions were also performed to reveal detailed information about their electronic structure and magnetic anisotropy, supporting the experimental observations. This study accentuates the mutual distortion of coordination geometry induced by flexibility of the ligand backbone with the simultaneous binding of two different metal ions.

This paper investigates the reactivity and optical properties of transition metal-incorporated organoantimony(V) clusters prepared by a solvothermal route. The detailed structural characterization of novel heterometallic M 2 Sb 4 oxo clusters is reported herein. Single crystal X-ray diffraction revealed the formation of hexanuclear organoantimony(V) based oxo clusters [( p -ClC 6 H 4 Sb) 4 V 2 (O) 2 (μ 3 -O) 2 (μ 2 -O) 2 ( t -BuPO 3 ) 4 (μ 2 -OCH 3 ) 4 ] (1), [M 2 ( p -iPr-C 6 H 4 Sb) 4 (μ 3 -O) 2 (μ 2 -O) 2 (μ 2 -OCH 3 ) 4 ( t -BuPO 3 ) 4 (py) 2 ]· x CH 3 OH, where M = Mn, x = 2 (2), Co, x = 1 (3), Ni, x = 2 (4) and Cu, x = 2 (5). The magnetic behaviour of the clusters was probed by magnetic susceptibility measurements. Optical absorption studies showed that bandgap reduction can be achieved by incorporating an appropriate transition metal into the homometallic Sb 6 oxo cluster.

The reaction between the 2-(1-(2,6-di(pyrazol-1-yl)-4-methylpyridyl)-4,5-(4,5-bis(propylthio)-tetrathiafulvalenyl)-1 H -benzimidazol-2-yl)-pyridine ligand (L), 1 equivalent of Ln(hfac) 3 ·2H 2 O/Dy(tta) 3 ·2H 2 O (hfac - = 1,1,1,5,5,5-hexafluoroacetylacetonate, tta - = 2-thenoyltrifluoroacetonate) and M(hfac) 2 ·2H 2 O leads to the formation of heteroleptic 3d-4f dinuclear complexes of formula [MLn(hfac) 5 (L)] n (M(II) = Cd, Zn, Co, Mn, Ni and Ln(III) = Dy, Yb, Nd) and [ZnDy(tta) 2 (hfac) 3 (L)]·(CH 2 Cl 2 ). Their X-ray structures reveal that the two coordination sites are occupied by one Ln(III) ion and one M(II) transition metal respectively. The M(II) ions are coordinated to the benzoimidazolylpyridine (bzip) moiety in a N 2 O 4 coordination sphere, while the Ln(III) ions are coordinated to the 2,6-di(pyrazol-1-yl)-4-pyridine (dpp) moiety in a N 3 O 6 surrounding. When Dy(III) ion is used a field-induced Single-Molecule Magnet (SMM) behavior is detected with a magnetic relaxation time slightly dependent to the nature of the vicinal divalent transition metal. On the other hand, when the Yb(III) is used, intense, moderated or quenched 2 F 5/2 → 2 F 7/2 NIR luminescence is observed when the Yb(III) ion is respectively associated with the Zn(II), Mn(II) and Ni(II)/Co(II) ion. The emission intensity can be modulated in function of the metal-to-ligand charge transfer and d-d transition intensities. The replacement of the divalent transition metal by a trivalent lanthanide leads to the formation of heteroleptic 4f-4f' dinuclear complexes of formula [Ln 2- x Ln' x (hfac) 6 (L)]· a (CH 2 Cl 2 )· b (C 6 H 14 ) and [Dy 1.11 Nd 0.89 (tta) 3 (hfac) 3 (L)]. The coordination selectivity is based on the radius. Among the 4f-4f' series, the Dy(III) derivatives displayed such ion in N 2 O 6 eight-coordinated sphere allowing the observation of SMM behavior. The three compounds [Dy 1.21 Nd 0.79 (hfac) 6 (L)]·2(CH 2 Cl 2 )·(C 6 H 14 ), [Yb 1.04 Nd 0.96 (hfac) 6 (L)] and [YbPr(hfac) 6 (L)] displayed respectively Nd(III), modarated Yb(III) and intense Yb(III) NIR emissions.

The effects of isotopic enrichment and magnetic dilution have been investigated in a heterobimetallic complex of formula [Zn 2 L 2 A DyCl 3 ]·2H 2 O ( A DyZn 2 ) (A = 162 and 163) presenting slow relaxation of the magnetization. Isotopic substitution for 162 Dy (I = 0) and 163 Dy (I = 5/2) leads to a shift in the relaxation times depending on the suppression or enhancement of the hyperfine interactions. The release of the dipolar interactions through magnetic dilution in a Y(iii)-based matrix enhances the slow relaxation of the magnetization and the visibility of the nuclear spin effect. A comparison of the hysteresis loop at 0.5 K for bulk and diluted analogues of pure isotopically enriched complexes suggested a role of the nuclear spin in the interaction between the active system and the matrix.

We hereby report a dinuclear Dy(iii) complex, [Dy(LH 3 )Cl 2 ] 2 ·2Et 2 O (1) (LH 4 = 2,3-dihydroxybenzylidene)-2-(hydroxyimino)propanehydrazide where both the metal centres are in a pentagonal bipyramidal (PBP) geometry with the axial positions being occupied by negatively charged Cl - ions. The complex as well as it's 10% diluted analogue (1 10 ) do not show zero-field SMM behaviour. However, in the presence of small optimum dc fields the slow relaxation of magnetization was displayed. The effective energy barrier for 1 10 at 800 Oe of applied field was extracted as 83(17) K with τ 0 = 2(4) × 10 -12 s. Through a combined experimental and ab initio electronic structure calculations studies we have thoroughly analysed the role of the ligand field around the Dy(iii), present in pentagonal bipyramidal geometry, in contributing to the slow relaxation of magnetization.

An alternative strategy for the synthesis of terpyridine based switchable molecular tweezers has been developed to incorporate anisotropic Mn(iii)-salphen complexes. The free ligand was synthesized using a building block strategy based on Sonogashira coupling reactions and was then selectively metalated with manganese in a last step. The conformation of the tweezers was switched from an open 'W' shaped form to a closed 'U' form by Zn(ii) coordination to the terpyridine unit bringing the two Mn-salphen moieties in close spatial proximity as confirmed by X-ray crystallography. An alternate switching mechanism was observed by the intercalation of a bridging cyanide ligand between the two Mn-salphen moieties that resulted in the closing of the tweezers. These dual stimuli are attractive for achieving multiple controls of the mechanical motion of the tweezers. A crystallographic structure of unexpected partially oxidized closed tweezers was also obtained. One of the two Mn-salphen moieties underwent a ligand-centered oxidation of an imino to an amido group allowing an intramolecular Mn-Oamide-Mn linkage. The magnetic properties of the manganese(iii) dimers were investigated to evaluate the magnetic exchange interaction and analyze the single molecule magnet behavior.

A family of mononuclear penta-coordinated CoII complexes, [Co(L)Cl2]·CH3OH (1), [Co(L)Br2] (2) and [Co(L)(NCS)2] (3) (where L is 1-mesityl-N,N-bis(pyridin-2-ylmethyl)methanamine) were synthesized and characterized. In these complexes, the neutral non-planar ligand, L, binds to three coordination sites around the metal center while two others are bound by anionic halide/pseudo halide ligands. The coordination geometry of the complexes is dictated by the coordinated anionic ligands. Thus, the coordination geometry around the metal ion is distorted trigonal bipyramidal for complexes 1 and 3, while it is distorted square pyramidal for complex 2. Ab initio CASSCF/NEVPT2 calculations on the complexes reveal the presence of an easy plane magnetic anisotropy with the D and E/D values being, 13.3 and 0.14 cm-1 for 1; 36.1 and 0.24 cm-1 for 2 and ±8.6 and 0.32 cm-1 for 3. These values are in good agreement with the values that were extracted from the experimental DC data. AC magnetic measurements reveal the presence of a field-induced slow relaxation of magnetization. However, clear maxima in the out-of-phase susceptibility curves were not observed for 1 and 3. For complex 2, peak maxima were observed when the measurements were carried out under an applied field of 1400 Oe which allowed an analysis of the dynamics of the slow relaxation of magnetization. This revealed that the relaxation is mainly controlled by the Raman and direct processes with the values of the parameters found to be: B = 0.77(15) s-1 K-6.35, n = 6.35(12) and A = 3.41(4) × 10-10 s-1 Oe-4 K-1 and m = 4 (fixed). The ab initio calculation which showed the multifunctional nature of the electronic states of the complexes justifies the absence of zero-field SIM behaviour of the complexes. The magnitude and sign of the D and E values and their relationship with the covalency of the metal-ligand bonds was analysed by the CASSCF/NEVPT2 as well as AILFT calculations.

A centro-symmetric binuclear compound of formula [Dy(L)·(CH3COO)2·(H2O)2]2 (1) was isolated from the reaction between the 2,4-dinitrobenzoate anion (L) and the tris(acetate) of Dy(iii). Single crystal diffraction studies reveal a μ1-κ2,η1:η1 chelating binding mode of L while the binuclear compound is formed by the two bridging (μ2-κ3,η1:η2) acetate anions. The nona-coordinated sphere of each Dy(iii) ion is filled with a chelating (κ2,η1:η1) acetate anion and two terminal water molecules. Static magnetic measurements combined with ab initio SA-CASSCF/RASSI-SO calculations lead to two intramolecular competitive interactions i.e. ferromagnetic exchange interactions (0.04 cm-1) and antiferromagnetic dipolar interactions (-0.5 cm-1). Finally, dynamic magnetic measurements revealed a Single-Molecule Magnet behaviour in a zero-applied magnetic field with an effective energy barrier Δ = 21.5(2) cm-1 and τ0 = 7(3) × 10-6 s through Orbach and Quantum Tunnelling of the Magnetization relaxation mechanisms.

Single crystal diffraction studies reveal the formation of the following 10 new complexes of lighter Ln(iii) ions with general formulas {[Ln(μ2-L1)3·(H2O)2]·H2O}n (Ln = Nd (1) and Eu (2)), [Nd(μ2-L2)2·(CH3COO)·(H2O)2]n (3), [Ln2(μ2-L2)5·(L2)·(H2O)4]n (Ln = Sm (4), Ce (5), and Pr (6)), [La2(μ2-L2)6·(H2O)3·(DMF)]n (7) (DMF = dimethylformamide), [Ln(μ2-L2)2·(L2)·(H2O)3]2 (Ln = Eu (8) and Gd (9)) and [Gd(L2)·(CH3COO)2·(H2O)2]2 (10), where L1 and L2 are anions of 3,5- and 2,4-dinitrobenzoic acid, respectively. Complexes 1-7 are 1D coordination polymers, while 8-10 are dinuclear complexes. The luminescence properties of Nd(iii) and Eu(iii) analogues displayed metal-centred emission with L1 exhibiting weak but more efficient sensitization than L2. A study of the magnetic properties of the compounds clearly demonstrated the field-induced single ion magnet behaviour of the Nd(iii) compounds 1 and 3. Their behaviour has been compared to previously reported analogous Nd(iii) complexes and the role of the lattice solvent and polymorphism on the magnetic behaviour has been evaluated.

The elaboration of multifunctional materials is a great challenge for the physical chemistry community and the studies of molecular materials exhibiting coexistence or synergy between two or more properties are very active. In particular, molecular compounds displaying electrical conductivity and magnetic interactions are currently the subject of intensive studies. Two approaches are now well-known and are explored. On the one hand, the interactions between mobile electrons of the organic network (π electrons) and localized electrons of paramagnetic transition metal (d electrons) take place through space. On the other hand, these interactions take place through covalent chemical bonds. In the latter, the probability to have significant interaction between π and d electrons is enhanced compared to the first approach. In this perspective article, we will give an overview of the known coordination complexes involving tetrathiafulvalene derivatives as ligands for paramagnetic 3d ions and we will describe their physical properties. If necessary, the coexistence or synergy between electrical conductivity, magnetism and other properties will be highlighted.

The tetrathiafulvalene based 2-immino-pyrazine derivative (TTF-CHN-2-pyz) () was synthesized and characterized. Its radical cation salt ( (+)PF(6)(-)) was prepared as single crystals by electrocrystallisation. (+)PF(6)(-) crystallizes in the triclinic P1 space group. Four 1 : 2 bis(hexafluoroacetylacetonate)M(ii) complexes coordinated with were prepared (M = Mn for , M = Co for , M = Cu for and M = Zn for ). Complex crystallizes in the monoclinic C2/c space group, complexes and crystallize in the triclinic space group P1. Two pyrazine N atoms from two different donors are coordinated in cis configuration for and trans configuration for and to the metallic ion of M(hfac)(2) (hfac(-)=hexafluoroacetylacetonate anion). The manganese atom adopts a pseudo-compressed octahedral geometry while the copper and the zinc ions adopt axially elongated octahedral geometries. Both crystal packing structures and electrochemical properties are appropriate for their potential use as starting molecular bricks for conducting and magnetic materials.

The reaction between [Ru(salen)(PPh3)Cl] and the 4-pyridyl-substituted nitronyl nitroxide radical (NITpPy) leads to the [Ru(salen)(PPh3)(NITpPy)](ClO4)(H2O)2 complex while the reaction with the azido anion (N3-) leads to the [Ru(salen)(PPh3)(N3)] complex 2 (where salen2- = N,N'-ethan-1,2-diylbis(salicylidenamine) and PPh3 = triphenylphosphine). Both compounds have been characterized by single crystal X-ray diffraction. The two crystal structures are composed by a [Ru(III)(salen)(PPh3)]+ unit where the Ru(III) ion is coordinated to a salen2- ligand and one PPh3 ligand in axial position. In 1 the Ru(III) ion is coordinated to the 4-pyridyl-substituted nitronyl nitroxide radical whereas in 2 the second axial position is occupied by the azido ligand. In both complexes the Ru(III) ions are in the same environment RuO2N3P, in a tetragonally elongated octhaedral geometry. The crystal packing of 1 reveals pi-stacking in pairs. While antiferromagnetic intermolecular interaction (J2 = 5.0 cm(-1)) dominates at low temperatures, ferromagnetic intramolecular interaction (J1 = -9.0 cm(-1)) have been found between the Ru(III) ion and the coordinated NITpPy.