Synthesis and Characterization of a Linear [Mn3(O2CMe)4(py)8]2+ Complex

Two new compounds that consist of the linear trinuclear manganese(II) cation [Mn3(O2CMe)4(py)8]2+ cocrystallizing with different counteranions (I3−, [1]; ClO4−, [2]) are reported. Complex 1 was prepared from the reaction of [Mn(O2CMe)2] · 4H2O with I2 in MeCO2H/py, whereas complex 2 was isolated from the reaction of [Mn3O(O2CMe)6(py)3] · py with [Mn(ClO4)2] · 6H2O in MeCN/py. The crystal structures of both compounds were determined by single crystal X-ray crystallography. Magnetic susceptibility studies that were performed in microcrystalline powder of 1 in the 2–300 K range revealed the presence of antiferromagnetic exchange interactions that resulted in an S = 5/2 ground spin state

(Z)-tert-Butyl 2-(4-amino-9H-fluoren-9-yl­idene)acetate

The title compound, C19H19NO2, obtained as an almost equimolar mixture (as shown by 1H NMR) with the E isomer through a Wittig reaction between 4-amino-9H-fluoren-9-one and the stabilized ylide Ph3P=CHCO2C(CH3)3, was obtained pure in the Z configuration following crystallization from toluene. The mol­ecule shows a planar arrangement of the ring system and the new double bond, whereas the carbonyl O atom forms a 45.1 (3)° dihedral angle with it. The mol­ecules are linked by N—H⋯O hydrogen bonds, forming cyclic structures with R 4 4(24) graph-set motifs. These motifs are connected to each other, giving rise to a sheet structure parallel to the ab plane. The linkage within the sheets is further enhanced by π–π stacking inter­actions between the fluorene units [centroid–centroid distance = 3.583 (2) Å]

Mononuclear and Dinuclear Manganese(II) Complexes from the Use of Methyl(2-pyridyl)ketone Oxime

The reactions of methyl(2-pyridyl)ketone oxime, (py)C(Me)NOH, with manganese(II) sulfate monohydrate have been investigated. The reaction between equimolar quantities of MnSO4 · H2O and (py)C(Me)NOH in H2O lead to the dinuclear complex [Mn2(SO4)2{(py)C(Me)NOH}4] · (py)C(Me)NOH, 1 · (py)C(Me)NOH, while employment of NaOMe as base affords the compound [Mn(HCO2)2{(py)C(Me)NOH}2] (2). The structures of both compounds have been determined by single crystal X-ray diffraction. In both complexes, the organic ligand chelates through its nitrogen atoms. The IR data are discussed in terms of the nature of bonding and the structures of the two complexes

(2E,4E,6E)-3-Methyl-7-(pyren-1-yl)octa-2,4,6-trienoic acid

The title compound, C25H20O2, was synthesized by a Wittig reaction between triphen­yl[1-(pyren-1-yl)eth­yl]phospho­nium bromide and ethyl (2E,4E)-3-methyl-6-oxohexa-2,4-dienoate, in the presence of n-butyl lithium, followed by saponification. It was obtained pure in the all-trans configuration following crystallization from ethyl acetate. The asymmetric unit contains two independent mol­ecules (A and B), which are arranged almost parallel to each other within the crystal structure. The triene chain is not coplanar with the pyrene ring system, forming dihedral angles of 52.8 (1) and 42.2 (1)° for mol­ecules A and B, respectively. Inter­molecular hydrogen bonds between the carboxyl groups of the mol­ecules link them into centrosymmetric pairs, AA and BB, each with the R 2 2(8) graph-set motif

Giant Heterometallic [Mn36Ni4]0/2− and [Mn32Co8] “Loops-of-Loops-and-Supertetrahedra” Molecular Aggregates

We report the synthesis, crystal structures and magnetic properties of the giant heterometallic [Mn36Ni4]2−/0 (compounds 1, 2)/[Mn32Co8] (compound 3) “loops-of-loops-and-supertetrahedra” molecular aggregates and of a [Mn2Ni6]2+ compound (cation of 4) that is structurally related with the cation co-crystallizing with the anion of 1. In particular, after the initial preparation and characterization of compound [Mn2Ni6(μ4-O)2(μ3-OH)3(μ3-Cl)3(O2CCH3)6(py)8]2+[Mn36Ni4(μ4-O)8(μ3-O)4(μ3-Cl)8Cl4(O2CCH3)26(pd)24(py)4]2− (1) we targeted the isolation of (i) both the cationic and the anionic aggregates of 1 in a discrete form and (ii) the Mn/Co analog of [Mn36Ni4]2− aggregate. Our synthetic efforts toward these directions afforded the discrete [Mn36Ni4] “loops-of-loops-and-supertetrahedra” aggregate [Mn36Ni4(μ4-O)8(μ3-O)4(μ3-Cl)8Cl2(O2CCH3)26(pd)24(py)4(H2O)2] (2), the heterometallic Mn/Co analog [Mn32Co8(μ4-O)8(μ3-O)4(μ3-Cl)8Cl2(μ2-OCH2CH3)2(O2CCH3)28(pd)22(py)6] (3) and the discrete [Mn2Ni6]2+ cation [Mn2Ni6(μ4-O)2(μ3-OH)4(μ3-Cl)2(O2CCH3)6(py)8](ClO4)(OH) (4). The structure of 1 consists of a mixed valence [Mn28IIIMn8IINi4II]2− molecular aggregate that contains two Mn8IIINi2II loops separated by two Mn6IIIMn4II supertetrahedral units and a [Mn2IIINi6II]2+ cation based on two [MnIIINi3II(μ4-O)(μ3-OH)1.5(μ3-Cl)1.5]4+ cubane sub-units connected through both mono- and tri-atomic bridges provided by the μ4-O2− and carboxylate anions. The structures of 2–4 are related to those of the compounds co-crystallized in 1 exhibiting however some differences that shall be discussed in detail in the manuscript. Magnetism studies revealed the presence of dominant ferromagnetic interactions in 1–3 that lead to large ground state spin (ST) values for the “loops-of-loops-and-supertetrahedra” aggregates and antiferromagnetic exchange interactions in 4 that lead to a low (and possibly zero) ST value. In particular, dc and ac magnetic susceptibility studies revealed that the discrete [Mn36Ni4] aggregate exhibits a large ST value ~ 26 but is not a new SMM. The ac magnetic susceptibility studies of the [Mn32Co8] analog revealed an extremely weak beginning of an out-of-phase tail indicating the presence of a very small relaxation barrier assignable to the anisotropic Co2+ions and a resulting out-of-phase ac signal whose peak is at very low T

[Pr(NO3)3L]: a mononuclear ten-coordinate lanthanide(III) complex with a tetradentate di-Schiff base

The novel praseodymium(III) complex [Pr(NO3)3L] (1), where L=N,N′-bis[1-(pyridin-2-yl)ethylidene]ethane-1,2-diamine, has been obtained by direct reaction of the Schiff base and the metal salt; the gadolinium(III) homologue has also been prepared and so far characterized only spectroscopically. The crystal structure resembles those reported for hexadentate macrocyclic Schiff bases

Zinc(II) and Nickel(II) Benzoate Complexes from the Use of 1-methyl-4,5-diphenylimidazole

Two new complexes, [Zn(O2CPh)2(L)2]⋅2MeOH  (⋅2MeOH) and [Ni2(O2CPh))4(L)2]⋅2MeCN  (⋅2MeCN), have been synthesized and characterized by X-ray analysis in the course of an ongoing investigation of the MII/X−/L[MII=Co,Ni,Cu,Zn; X−=Cl−,Br−,I−,NCS−,NO−3,N−3,PhCO−2; L=1-methyl-4,5-diphenylimidazole] reaction system, aiming at understanding and assessing the relative strength and the way in which the intermolecular interactions control the supramolecular organization of these compounds. In the mononuclear complex ⋅2MeOH, the benzoate ion acts as a monodentate ligand resulting in a distorted tetrahedral N2O2 coordination environment. Complex ⋅2MeCN exhibits a dinuclear paddle-wheel structure; each NiII has a square pyramidal NiNO4 chromophore with four benzoate oxygens in the basal plane and the pyridine-type nitrogen atom of one ligand L at the apex. The structure of ⋅2MeOH is stabilized by intramolecular - interactions between aromatic rings of adjacent 4,5-diphenylimidazole moieties; it is a feature also evidenced in similar compounds of the type [MX2L2]

A Mn-15 single-molecule magnet consisting of a supertetrahedron incorporated in a loop

International audienceTwo new Mn-15 clusters consisting of a supertetrahedron which is incorporated in a loop are reported. The reactions of [Mn(O2CEt)(2)]center dot 2H(2)O with the diols 1,3-propanediol (H(2)pd) or 2-methyl-1,3-propanediol (H(2)mpd) in the presence of KX (X = CN-, Cl-, Br-, NO3-, ClO4-, OCN-, SCN-) afforded compounds [Mn15K(mu(4)-O)(4)(O2CEt)(11)(pd)(12)(py)(2)] (1) and [Mn15K(mu(4)-O)(4)(O2CEt)(11)(mpd)(12)(py)(2)] (2). The structural core of 1 and 2 consists of a Mn-11 loop and a Mn9K supertetrahedron sharing a Mn-5 triangle. To the best of our knowledge, the structural motif of a supertetrahedron incorporated in a loop appears for the first time in metal cluster chemistry. Variable-temperature, solid-state direct current (dc) magnetic susceptibility studies in the 300-5 K range showed that the chi T-M value increases with decreasing T suggesting the existence of predominant ferromagnetic exchange interactions and a relatively large ground state spin. This was confirmed by field-variable temperature magnetization measurements which were fitted using a matrix diagonalization method to give S similar to 23/2, g = 1.92(1) and D = -0.071(2) cm(-1). In addition, compound 1 displays frequency-dependent alternating current (ac) signals suggesting single-molecule magnetism (SMM) behaviour. This was proven by magnetization vs. dc field sweeps on single-crystals of 1 center dot 0.7py center dot 1.3MeCN, which displayed sweep rate- and temperature-dependent hysteresis loop