Selective Self-Assembly of a Rectangular Ruthenium Supramolecule from an Unsymmetrical Bridging Unit.

Herein, we report the synthesis of an unsymmetrical diruthenium bridging unit containing a multidentate oxamate ligand and the subsequent formation of a rectangular supramolecule. The reaction of oxamate 1, 2-((4-bromo-2,6-dimethylphenyl)amino)-2-oxo-acetic acid, and [(p-cymene)RuCl2]2 affords a novel unsymmetrical diruthenium acceptor clip 2, where two ruthenium metal centers are ligated with either [O,O] or [N,O]. The molecular clip 2 and bipyridine donor self-assemble to form two-dimensional rectangular supramolecule 3. Self-assembly can produce seven possible isomers depending on the position of the substituted bromoaryl groups. However, 1H NMR spectroscopic investigation indicated only two different isomers in the reaction mixture. A single isomer is isolated via crystallization, and X-ray crystallography confirms that the product is a C1 symmetric two-dimensional rectangular supramolecule, in which two bromoaryl groups are located in the farthest position from each other. Theoretical calculations suggest that the self-assembly of supramolecule 3 occurred via 1:1 adducts of the diruthenium molecular clip and bipyridine as an intermediate to predominantly form a single isomer.

C-F Bond Activation by a Saturated N-Heterocyclic Carbene: Mesoionic Compound Formation and Adduct Formation with B(C6 F5 )3.

The reaction of SIPr, [1,3-bis(2,6-diisopropylphenyl)-imidazolin-2-ylidene] (1), with C6 F6 led to the formation of an unprecedented mesoionic compound (2). The formation of 2 is made accessible by deprotonation of the SIPr backbone with simultaneous elimination of HF. The C-F bond para to the imidazolium ring in 2 is only of 1.258(4) Å, which is the one of the shortest structurally authenticated C-F bonds known to date. The liberation of HF during the reaction is unequivocally proved by the addition of one more equivalent of SIPr, which leads to the imidazolium salt with the HF2 - anion. To functionalize 2, the latter reacted with B(C6 F5 )3 to give an unusual donor-acceptor compound, where the fluoride atom from the C6 F5 moiety coordinates to B(C6 F5 )3 and the carbanion moiety remains unaffected. Such coordination susceptibility of the fluoride atom of a nonmetallic system to a main-group Lewis acid (Fnon-metal →BR3 ) is quite unprecedented.

Unique Ruthenium Bimetallic Supramolecular Cages From C4-Symmetric Tetrapyridyl Metalloligands.

The self-assembly of C4-symmetric tetrapyridyl metalloligands containing Fe or Co and diruthenium electron acceptors by means of dative coordination bonding led to the formation of six different heterobimetallic supramolecules. All complexes were characterized by X-ray crystallography, ESI mass spectrometry, and 1H NMR (in the case of diamagnetic systems) spectroscopy. The bridging units in the diruthenium complexes greatly influenced the geometrical preference of the supramolecular structures, resulting in the formation of different architectures, namely A4D2 or A6D3 (A = acceptor, D = donor). Depending on the bridging unit, A4D2 tetragonal prism, A4D2 molecular tweezer, or A6D3 triple-decker complexes were obtained selectively. The self-assembly of an unexpected triple-decker type Ru12Fe3 heterobimetallic species was also observed.

Dangling and Hydrolyzed Ligand Arms in [Mn3] and [Mn6] Coordination Assemblies: Synthesis, Characterization, and Functional Activity.

Two flexible, branched, and sterically constrained di- and tripodal side arms around a phenol backbone were utilized in ligands H3L1 and H5L2 to isolate {Mn6} and {Mn3} coordination aggregates. 2,6-Bis{(1-hydroxy-2-methylpropan-2-ylimino)methyl}-4-methylphenol (H3L1) gave trinuclear complex [Mn3(µ-H2L1)2(µ1,3-O2CCH3)4(CH3OH)2](ClO4)2·4CH3OH (1), whereas 2,6-bis[{1-hydroxy-2-(hydroxymethyl)butan-2-ylimino}methyl]-4-methylphenol (H5L2) provided hexanuclear complex [Mn6(µ4-H2L2)2(µ-HL3)2(µ3-OH)2(µ1,3-O2CC2H5)4](ClO4)2·2H2O (2). Binding of acetates and coordination of {H2L1}- provided a linear MnIIIMnIIMnIII arrangement in 1. A MnIII6 fused diadamantane-type assembly was obtained in 2 from propionate bridges, coordination of {H2L2}3-, and in situ generated {HL3}2-. The magnetic characterization of 1 and 2 revealed the properties dominated by intramolecular anti-ferromagnetic exchange interactions, and this was confirmed using density functional theory calculations. Complex 1 exhibited field-induced slow magnetic relaxation at 2 K due to the axial anisotropy of MnIII centers. Both the complexes show effective solvent-dependent catechol oxidation toward 3,5-di-tert-butylcatechol in air. The catechol oxidation abilities are comparable from two complexes of different nuclearity and structure.

Anion coordination selective [Mn3] and [Mn4] assemblies: synthesis, structural diversity, magnetic properties and catechol oxidase activity.

Syntheses, crystal structures, magnetic properties and catechol oxidation behavior are presented for [Mn3] and [Mn4] aggregates, [MnMn(II)(O2CMe)4(dmp)2(H2O)2]·2H2O (1·2H2O), [MnMn(II)(O2CCH2Cl)4(dmp)2(H2O)2]·H2O·MeOH (2·H2O·MeOH), [Mn(µ3-O)(dmp)4(µ-DMSO)(N3)(DMSO)(H2O)]ClO4·DMSO (3·ClO4·DMSO), and [Mn(µ3-O)(dmp)4(µ-DMSO)(ClO4)(DMSO)(H2O)]ClO4·DMSO (4·ClO4·DMSO), developed with single type ligand H2dmp, 2-[(2-hydroxy-1,1-dimethyl-ethylimino)-methyl]-phenol. The successful isolation of 1-4 resulted from a systematic exploration of the effect of Mn(II) salts, added carboxylates, Mn/H2dmp ratio, presence of azide, and other reaction conditions. The cores of 1 and 2 are similar and consist of a linear Mn(III)Mn(II)Mn(III) unit in a carboxylate and H2dmp environment, revealing a central Mn(II) ion in a different environment and terminal Mn(III) ions available for the introduction of structural and magnetic anisotropy to the system. The cores of 3 and 4 are also similar and consist of a distorted incomplete-adamantane type Mn4 coordination assembly in a carboxylate-free environment built on a triangular [Mn(µ3-O)] unit. The magnetic behavior of complexes 1-3 is dominated by antiferromagnetic exchange coupling that results in ground state spin values of S = 3/2 for 1 and 2 and S = 0 for 3. In solution, all four complexes 1-4 show catechol oxidation activity towards 3,5-DTBC. The catalytic activity for the oxidation of 3,5-DTBC in air followed the order 4 < 3 < 1 < 2.

Correction: Two types of nitrito support for µ4-oxido-bridged [Cu4] complexes: synthesis, crystal structures, magnetic properties and DFT analysis.

Correction for 'Two types of nitrito support for µ4-oxido-bridged [Cu4] complexes: synthesis, crystal structures, magnetic properties and DFT analysis' by Moumita Pait, et al., Dalton Trans., 2015, 44, 6107-6117.

A new family of Ni4 and Ni6 aggregates from the self-assembly of [Ni2] building units: role of carboxylate and carbonate bridges.

Carboxylato (R = (t)Bu and Et) and carbonato bridges have been utilized for nickel(II)-based aggregates [Ni4(µ-H2L)2(µ3-OH)2(µ1,3-O2CBu(t))2](NO3)2·H2O·2DMF (1·H2O·2DMF), Ni4(µ-(hy)HL)2(µ3-OMe)2(µ1,1-N3)2(µ1,3-O2CEt)2]·4H2O (2·4H2O), and Ni6(µ4-L)(µ3-L)2(µ6-CO3)(H2O)8](ClO4)·9H2O (3·9H2O). Building blocks [Ni2(µ-H2L)](3+), [Ni2(µ-(hy)HL)](3+), and [Ni2(µ-L)](+) originating from [Ni2(µ-H2L)](3+) have been trapped in these complexes. The complexes have been characterized by X-ray crystallography, magnetic measurements, and density functional theory (DFT) analysis. In 1, the magnetic interactions are transmitted through the µ3-phenoxido/µ3-hydroxido/syn-syn-(t)BuCO2(-), µ3-phenoxido/µ3- hydroxido, and double µ3-phenoxido/double µ3-hydroxido bridges with J = +11.4 cm(-1), J1 = -2.1 cm(-1), and J2 = -2.8 cm(-1), respectively. In 2, the interactions are ferromagnetic, with J1 = +27.5 cm(-1), J2 = +20.62 cm(-1), and J3 = +1.52 cm(-1) describing the magnetic couplings through the µ-phenoxidoo/µ3-methoxido, µ-azido/µ3-methoxido, and µ3-methoxido/µ3-methoxido exchange pathways, respectively. Complex 3 gives J1 = -3.30 cm(-1), J2 = +1.7 cm(-1), and J3 = -12.8 cm(-1) for exchange pathways mediated by µ-phenoxido/µ-carbonato, µ-alkoxido/µ-alkooxido/µ-syn-syn-carbonato, and the µ-phenoxido/µ-carbonato, respectively. Interestingly, 1 and 3 below 20 K and 35 K, respectively, show an abrupt increase of the χMT product to reach a magnetic-field-dependent maximum, which is associated with a slightly frequency-dependent out-of-phase alternating-current peak. DFT calculations have also been performed on 1-3 to explain the exchange interaction mechanisms and to support the magnitude and sign of the magnetic coupling constants between the Ni(II) ions.

Two types of nitrito support for µ4-oxido-bridged [Cu4] complexes: synthesis, crystal structures, magnetic properties and DFT analysis.

Novel nitrito supported and µ4-oxido bridged Cu(II) aggregates have been found in two tetranuclear complexes, [Cu4(µ4-O)L2(µ(1,3)-ONO)4] (1) and [Cu4(µ4-O)L2(µ(1,3)-OAc)2(µ1,2-NO2)2] (2), of the chiral Schiff base HL (HL = 4-methyl-2,6-bis-(1-phenyl-ethylimino)-methylphenol). The structures contain either in situ generated or externally added peripheral µ-nitrito groups, in κ(2)O/O and κ(2)N/O bridging modes. Four NO2(-) bridges in 1 and two AcO(-) co-ligands along with two NO2(-) bridges in 2 are essential for the stabilization of these tetranuclear aggregates. The complexes have been characterized by X-ray crystal structure determination, spectroscopic and magnetic measurements, and density functional theory (DFT) analysis. They are formed from the assembly of two [Cu2L](3+) fragments around a water-derived oxido ligand under the control of nitrite or mixed nitrite/acetate bridges. Variable temperature magnetic susceptibility measurements reveal strong intramolecular antiferromagnetic exchange interactions within the tetranuclear clusters to yield S(T) = 0 ground state. The capacity of the two different nitrite bridging modes to mediate magnetic coupling has been examined through measurements and numerical fitting procedures, and rationalized by means of DFT calculations.

A dodecanuclear copper(II) cage self-assembled from six dicopper building units.

Reaction of the dinucleating phenol-based ligand, H3bpmp (2,6-bis-[(3-hydroxy-propylimino)-methyl]-4-methyl-phenol), with Cu(2+) ions in the presence of a hybrid base (NEt3 and NaN3) necessary for the in situ generation of required numbers of hydroxido ions, results in the formation of a novel NO3(-) capped and HO(-) supported {Cu12} coordination complex {Cu6(µ3-OH)3(µ3-Hbpmp)3(µ3-NO3)}2(NO3)2(OH)2·2H2O·2MeOH (1). When the components are combined in right proportions (metal : ligand : NEt3 : NaN3 = 2 : 1 : 3 : 2) in MeOH, twelve Cu(2+) ions assemble in a cuboctahedral geometry, containing six square and eight triangular faces around a considerable void space. Six of the eight [Cu3] triangular faces are bound by the six Hbpmp(2-) ligands with six free pendant propanol arms around the central hexagonal plane. X-ray structure determination indicates new geometrical features for the core formation and reveals the face-capping potential of the H3bpmp ligand for the growth of a cuboctahedral coordination cage with the support of anions like HO(-) and NO3(-). The experimentally observed (J/kB = -173 K) strong antiferromagnetic coupling within the Cu12 complex has been justified by the DFT calculations.

Self-assembly of a [Ni8] carbonate cube incorporating four µ4-carbonato linkers through fixation of atmospheric CO2 by ligated [Ni2] complexes.

The communication reports the synthesis, characterization, and magnetic behavior of a novel µ4-carbonato supported and imidazole capped ligated nickel cage [Ni8(µ-H2bpmp)4(µ4-CO3)4(ImH)8](NO3)4·2H2O (1) through self-assembly of ligand bound ferromagnetic Ni2 building blocks. Structural analysis indicates newer geometrical features for the coordination cage formation and dominant interdimer antiferromagnetic coupling resulting in a diamagnetic ground state.