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The Cu(2+)-mediated self-assembly of oxamato-based ligands derived from either the (S)- or (R)-enantiomers of the amino acid valine leads to the formation of two antiferromagnetically coupled homochiral anionic hexacopper(II) wheels in the presence of templating tetramethylammonium countercations.

Two distinct one-dimensional (1) and two-dimensional (2) mixed-metal-organic polymers have been synthesized by using the "complex-as-ligand" strategy. The structure of 1 consists of isolated ladderlike Mn(II)(2)Cu(II)(2) chains separated from each other by neutral Mn(II)(2) dimers, whereas 2 possesses an overall corrugated layer structure built from additional coordinative interactions between adjacent Mn(II)(2)Cu(II)(2) ladders. Interestingly, 1 and 2 show overall ferri- and antiferromagnetic behavior, respectively, as a result of their distinct crystalline aggregation in the solid state.

This perspective review shows how the coordination chemistry approach to magnetic wires based on dinuclear copper(II) complexes with rodlike aromatic oligomers (RAOs) as extended π-conjugated spacers can be extended to the design and synthesis of a novel class of metallo-carbon nanostructures (MCNs) with polycyclic aromatic hydrocarbons (PAHs) as illustrative examples of advanced magnetic nanodevices for single-molecule spintronics and quantum computing nanotechnologies. In this pursuit, two opposite but complementary ways have been explored: (i) the preparation of synthetic models through the skillful organic synthesis of tailor-made diamine-functionalized RAOs and PAHs as bridging ligands for experimental investigation of their single-molecule electron exchange (EE) and electron transport (ET) or quantum interference (QI) and quantum coherence (QC) properties, or (ii) their theoretical prediction with the aid of first-principle density functional (DFT) and time-dependent density functional (TDDFT) theories on appropriate models from chemists' creative imagination. [ABSTRACT FROM AUTHOR]

Dinuclear copper(II) complexes of the metallacyclophane-type, (nBu4N)4[Cu2(2,6-anba)2] (1) and (nBu4N)4[Cu2(1,5-naba)2]·4H2O (2) with photoactive 2,6-anthracene-(2,6-anba) and 1,5-naphthalenebis(oxamate) (1,5-naba) bridging ligands, are reported. They undergo a thermally reversible, solid-state photomagnetic (ON/OFF) switching between the moderately strong antiferromagnetically coupled dicopper(II) species and the corresponding magnetically uncoupled [4+4] photocycloaddition product. Density functional calculations give further insights on the intramolecular (“pseudo-bimolecular”) photocycloaddition reaction of the two facing 2,6-anthracene or 1,5-naphthalene spacers in this novel family of dicopper(II) oligoacenophanes. The unique ability of oligoacenes as photoswitchable antiferromagnetic wires between two CuII ions separated by relatively long intermetallic distances could be the basis for the development of new kinds of molecular spintronic devices, referred to as molecular magnetic switches. [ABSTRACT FROM AUTHOR]

Highlights: [•] New consecutive post-functionalization method for the coordination of catalytically active metals in MOFs. [•] High Cu loadings can be achieved with high activity in click chemistry catalysis. [•] Immobilized gold nanoparticles, very uniform size, ∼2nm, can be encapsulated in MIL-101(Cr). [•] Stability in benzyl alcohol oxidation is superior to Au/Al2O3 commercial catalyst. [Copyright &y& Elsevier]

Double-stranded anionic dinuclear copper(II) metallacyclic complexes of the paracyclophane type [Cu2L2]4− have been prepared by the CuII-mediated self-assembly of different para-phenylenebis(oxamato) bridging ligands with either zero-, one-, or four-electron-donating methyl substituents (L= N, N′- para-phenylenebis(oxamate) (ppba; 1), 2-methyl- N, N′- para-phenylenebis(oxamate) (Meppba; 2), and 2,3,5,6-tetramethyl- N, N′- para-phenylenebis(oxamate) (Me4ppba; 3)). These complexes have been isolated as their tetra- n-butylammonium ( 1 a- 3 a), lithium(I) ( 1 b- 3 b), and tetraphenylphosphonium salts ( 1 c- 3 c). The X-ray crystal structures of 1 a and 3 c show a parallel-displaced π-stacked conformation with a smaller deviation from perpendicularity between the two benzene rings and the basal planes of the square planar CuII ions when increasing the number of methyl substituents (average dihedral angles ( ϕ) of 58.72(7) and 73.67(5)° for 1 a and 3 c, respectively). Variable-temperature (2.0-300 K) magnetic-susceptibility measurements show an overall increase of the intramolecular antiferromagnetic coupling with the number of methyl substituents onto the para-phenylene spacers (− J=75-95, 100-124, and 128-144 cm−1 for 1 a- c, 2 a- c, and 3 a- c, respectively; H=− J S1× S2). Cyclic voltammetry (CV) measurements show a reversible one-electron oxidation of the double polymethyl-substituted para-phenylenediamidate bridging skeleton at a relatively low formal potential that decreases with the number of methyl substituents ( E1=+0.33, +0.24, and +0.15 V vs. SCE for 1- 3, respectively). The monooxidized dicopper(II) π-radical cation species 3′ prepared by the chemical oxidation of 3 with bromine exhibits intense metal-to-ligand charge-transfer (MLCT) transitions in the visible and near-IR ( λmax=595 and 875 nm, respectively) regions together with a rhombic EPR signal with a seven-line splitting pattern due to hyperfine coupling with the nuclear spin of the two CuII ions. Density functional (DF) calculations for 3′ evidence a characteristic iminoquinonoid-type short-long-short alternating sequence of CN and CC bonds for both tetramethyl- para-phenylenediamidate bridges and a large amount of spin density of negative sign mainly delocalized along each of the four benzene C atoms directly attached to the amidate N atoms, which is in agreement with a fully delocalized π-stacked monoradical ligand description. Hence, the spins of the two CuII ions ( SCu=1/2) that are antiparallel aligned in 3 (OFF state) become parallel in 3′ (ON state). Further developments may be then envisaged for this new permethylated dicopper(II) paracyclophane with a redox noninnocent ligand as a prototype for molecular magnetic electroswitch. [ABSTRACT FROM AUTHOR]

Abstract: A novel series of copper(II) complexes of formula [Cu(tren)(mpda)](ClO4)2 ·1/2H2O (1), [Cu2(tren)2(mpda)](ClO4)4 ·2H2O (2), and [Cu2(tren)2(ppda)](ClO4)4 ·2H2O (3) containing the tetradentate tris(2-aminoethyl)amine (tren) terminal ligand and the potentially bridging 1,n-phenylenediamine [n =3 (mpda) and 4 (ppda)] ligand have been prepared and spectroscopically characterized. X-ray diffraction on single crystals of 1 and 3 show the presence of mono- (1) and dinuclear (3) copper(II) units where the mpda (1) and ppda (3) ligands adopt terminal monodentate (1) and bridging bis(monodentate) (3) coordination modes toward [Cu(tren)]2+ cations with an overall non-planar, orthogonal disposition of the phenylene group and the N–Cu–N threefold axis of the trigonal bipyramid of each copper(II) ion [values of the Cu–N–C–C torsion angle in the range of 50.8(3)–79.2(2) (1) and 80.9(2)–86.5(2)° (3)]. Variable-temperature magnetic susceptibility measurements on the dinuclear complexes 2 and 3 show the occurrence of moderate ferromagnetic (J =+8.3cm−1, 2) and strong antiferromagnetic (J =−51.4cm−1, 3) couplings between the two copper(II) ions across the meta- and para-phenylenediamine bridges, leading to S =1 (2) and S =0 (3) ground spin states [H =−J S1 · S2 with S 1 = S 2 = S Cu =1/2]. Density functional theory (DFT) calculations on the triplet (2) and broken-symmetry (BS) singlet (3) ground spin states, support the occurrence of a spin polarization mechanism for the propagation of the exchange interaction through the predominantly π-type orbital pathway of the 1,n-phenylenediamine bridge. Finally, a new magneto-structural correlation between the magnitude of the magnetic coupling (J) and the Cu–N–C–C torsion angle has been found which reveals the role of σ- versus π-type orbital pathways in the modulation of the magnetic coupling for m- and p-phenylenediamine-bridged dicopper(II) complexes. [Copyright &y& Elsevier]

Abstract: Two novel dinuclear copper(II) complexes of formulae [Cu2(tren)2(bpda)](ClO4)4 (2) and [Cu2(tren)2(tpda)](ClO4)4 (3) containing the tripodal tris(2-aminoethyl)amine (tren) terminal ligand and the 4,4′-biphenylenediamine (bpda) and 4,4″-p-terphenylenediamine (tpda) bridging ligands have been synthesized and structurally, spectroscopically, and magnetically characterized. Their experimentally available electronic spectroscopic and magnetic properties have been reasonably reproduced by DFT and TDDFT calculations. Single crystal X-ray diffraction analysis of 2 shows the presence of dicopper(II) cations where the bpda bridging ligand adopts a bismonodentate coordination mode toward two [Cu(tren)]2+ units with an overall non-planar, orthogonal anti configuration of the N–Cu–N threefold axis of the trigonal bipyramidal CuII ions and the biphenylene group. The electronic absorption spectra of 2 and 3 in acetonitrile reveal the presence of four moderately weak d–d transitions characteristic of a slightly distorted trigonal bipyramid stereochemistry of the CuII ions. TDDFT calculations on 2 identify these transitions as those taking place between the four lower-lying, doubly occupied a 2 (d yz )2, b 2 (d xz )2, b 1 (d xy )2, and a 1 ()2 orbitals and the upper, singly occupied a 1 ()1 orbital of each trigonal bipyramidal CuII ion. Variable-temperature magnetic susceptibility measurements of 2 and 3 show the occurrence of moderate (J =−8.5cm−1) to weak intramolecular antiferromagnetic couplings (J =−2.0cm–1) [H =−J S1 ·S2 with S 1 = S 2 = S Cu =½] inspite of the relatively large copper–copper separation across the para-substituted biphenylene- (r =12.3Å) and terphenylenediamine (r =16.4Å) bridges, respectively. DFT calculations on 2 and 3 support the occurrence of a spin polarization mechanism for the propagation of the exchange interaction between the two unpaired electrons occupying the orbital of each trigonal bipyramidal CuII ion through the predominantly π-type orbital pathway of the oligo-p-phenylenediamine bridges, as reported earlier for the parent compound [Cu2(tren)2(ppda)](ClO4)4·2H2O (1) with the 1,4-phenylenediamine (ppda) bridging ligand. Finally, a rather slow exponential decay of the antiferromagnetic coupling (–J) with the number of phenylene repeat units, –(C6H4) n – (n =1–3), has been found both experimentally and theoretically along this series of oligo-p-phenylenediamine-bridged dicopper(II) complexes. These results further support the ability of linear π-conjugated oligo-p-phenylene spacers to transmit the exchange interaction between the unpaired electrons of the two CuII centers with intermetallic distances in the range of 7.5–16.4Å. [Copyright &y& Elsevier]

This perspective review shows how the coordination chemistry approach to magnetic wires based on dinuclear copper(II) complexes with rodlike aromatic oligomers (RAOs) as extended π-conjugated spacers can be extended to the design and synthesis of a novel class of metallo-carbon nanostructures (MCNs) with polycyclic aromatic hydrocarbons (PAHs) as illustrative examples of advanced magnetic nanodevices for single-molecule spintronics and quantum computing nanotechnologies. In this pursuit, two opposite but complementary ways have been explored: (i) the preparation of synthetic models through the skillful organic synthesis of tailor-made diamine-functionalized RAOs and PAHs as bridging ligands for experimental investigation of their single-molecule electron exchange (EE) and electron transport (ET) or quantum interference (QI) and quantum coherence (QC) properties, or (ii) their theoretical prediction with the aid of first-principle density functional (DFT) and time-dependent density functional (TDDFT) theories on appropriate models from chemists' creative imagination. [ABSTRACT FROM AUTHOR]

We report the synthesis, crystal structure, and magnetic characterization of a novel two-dimensional copper(II)–dysprosium(III) coordination polymer of formula [LiI(OH 2) 4 ] 2 [DyIIICuII 2 (Me 2 pma) 4 Cl(H 2 O)] . 4H 2 O (1) [Me 2 pma = N -2,6-dimethylphenyloxamate]. Compound 1 was obtained using the mononuclear anionic complex [CuII(Me 2 pma) 2 ]2–, as a bis(bidentate) metalloligand toward solvated dysprosium(III) cations, and it shows a square [DyIIICuII 2 ] layered structure of (44.62) net topology. Interestingly, the combination of two factors, the well-known efficiency of oxamato ligands to transmit strong magnetic couplings between neighboring atoms and such structural topology, is responsible for the observation of a ferromagnetic interaction between copper(II) and dysprosium(III) cations and a magnetic ordering (T C = 7.5 K), paving the way for the obtention of novel future examples of the still very scarce magnetically ordered lanthanide-based coordination polymers. Image 1 [ABSTRACT FROM AUTHOR]

• A Cu-catalyzed 100% atom–efficient amidation and esterification reaction based on the reaction of cyclopropenones with amines or alcohols, is shown. • Both soluble and solid Cu catalysts are catalytically competent, and a Cu-containing metal–organic framework (MOF) is particularly active and reusable. • The reaction can be performed in a variety of solvents and reaction conditions, including water at different pHs, which can be defined as a click reaction. • A modular reactivity pattern (alkyl amines >> alkyl alcohols >> phenols >> aromatic amines) enables to design orthogonal and one–pot reactions on well–defined catalytic multimetal–MOFs (M–MOFs, M= Cu, Ni, Pd), to easily functionalize the resulting cinnamides and cinnamic esters to more complex molecules. Amides and esters are prevalent chemicals in Nature, industry and academic laboratories. Thus, it is not surprising that a plethora of synthetic methods for these compounds has been developed along the years. However, these methods are not 100% atom economical and generally require harsh reagents or reaction conditions. Here we show a "spring–loaded", 100% atom–efficient amidation and esterification protocol which consists in the ring opening of cyclopropenones with amines or alcohols. Some alkyl amines react spontaneously at room temperature in a variety of solvents and reaction conditions, including water at different pHs, while other alkyl amines, aromatic amines and alcohols react in the presence of catalytic amounts of simple Cu2+ salts or solids. A modular reactivity pattern (alkyl amines >> alkyl alcohols >> phenols >> aromatic amines) enables to design orthogonal and one–pot reactions on well–defined catalytic Multimetal–Organic Frameworks (M–MOFs, M= Cu, Ni, Pd), to easily functionalize the resulting cinnamides and cinnamic esters to more complex molecules. The strong resemblance of the amidation and esterification reaction conditions here reported with the copper–catalyzed azide–alkyne cycloaddition (CuAAC) allows to define this fast, clean and flexible protocol as a click reaction. [Display omitted] [ABSTRACT FROM AUTHOR]