Cyanide-bridged coordination polymers constructed from lanthanide ions and octacyanometallate building-blocks

A new series of cyanide-bridged assemblies, {KH[Ln2(2,3-pzdc)2(CH3OH)(H2O)7][M(CN)8]}·5H2O (Ln3+ = Nd, Gd, Tb, and Dy; M4+ = Mo and W), were synthesised by self-assembling lanthanide ions and octacyanometallate ions in the presence of pyrazine-2,3-dicarboxylic acid (2,3-H2pzdc). These compounds have a 3D structure in which octagon-like Ln4M4(CN)8 rings are connected through a second Ln3+ center via the carboxylate groups of one 2,3-pzdc. The resulting 1D channels are filled with K+ ions and lattice water molecules. The temperature and field dependent magnetization studies as well as ab initio calculations indicate weak ferromagnetic interactions between the Gd3+ ions within the GdMo compound whilst no magnetic interactions exist in GdW analogues. The magnetic properties of Nd3+, Tb3+ and Dy3+ compounds are strongly dominated by the magnetic anisotropy of the lanthanide ions, irrespective of the octacyanometallate building-block used

Mixed component metal-organic frameworks: Heterogeneity and complexity at the service of application performances

The synthesis of mixed-component metal-organic frameworks (MOFs) –including multivariate MOFs (MTV-MOFs), multicomponent MOFs, mixed-metals MOFs and mixed-ligands and metals MOFs– is becoming a very active research field. This is mainly based on the unique possibilities these materials offer to incorporate multiple functionalities and in how this heterogenity and complexity is translated in unexpected properties, which are not just the sum of each component. This review critically encompasses the progress made in this field, covering the synthetic approaches, and specially focusing on the current reported applications –such as gas storage and separation, catalysis, luminescence, conductivity, biological ones and water remediation. It also raises, as a perspective, some of the challenges the field has to overcome to reach their full-potential, and through two applications –(bio)enzymatic catalysis and synthesis of heterometallic subnanometric clusters and nanoparticles–, as exemplary cases, present some promising ways to take advantage of the intrinsic properties of mixed-components MOFs to make a breakthrough on the respective fields of application.This work was supported by the Ministero dell’Istruzione, dell’Università e della Ricerca (Italy), the Natural Science Foundation of Ningxia Province (China) (2020AAC02005) and the MINECO (Spain) (Projects PID2019–104778GB–I00, CTQ 2017–86735–P, RTC–2017–6331–5, Severo Ochoa program SEV–2016–0683 and Excellence Unit “Maria de Maeztu” CEX2019–000919–M). D.A. acknowledges the financial support of the Fondazione CARIPLO / “Economia Circolare: ricerca per un futuro sostenibile” 2019, Project code: 2019–2090, MOCA. Thanks are also extended to the “2019 Post–doctoral Junior Leader–Retaining Fellowship, la Caixa Foundation (ID100010434 and fellowship code LCF/BQ/PR19/11700011)”, the “Ramon y Cajal Programme” and “Subvenciones concedidas a la excelencia científica de juniors investigadores, SEJI/2020/034” (J. F.–S.). E.P. acknowledges the financial support of the European Research Council under the European Union's Horizon 2020 research and innovation programme / ERC Grant Agreement No 814804, MOF–reactors

A dinuclear manganese(III) and a rare pentanuclear manganese(III) compound with a phenol-pyrazole ligand

Reacting Mn(ClO4)2·6H2O and H2phpzEt (H2phpzEt = 5(3)-(2-hydroxyphenyl)-3(5)-ethylpyrazole) in methanol in the presence of sodium hydroxide yields the compound [Mn2(HphpzEt)4(H2O)2](ClO4)2 (1). The pentanuclear [Mn5(μ3-O)2(HphpzEt)3(phpzEt)3(OCH3)(HOCH3)2(O2CPh)] (2) is obtained when performing a similar reaction with Mn(O2CPh)2·2H2O. Compound 1 consists of a symmetric dinuclear manganese(III) cationic unit, [Mn2(HphpzEt)4(H2O)2]2+ with two non-coordinated perchlorate anions. Compound 2 is a rare pentanuclear complex containing all the manganese ions in the oxidation state III and it also has μ3-oxido ligands. Temperature- and field-dependent magnetization studies indicate dominant antiferromagnetic interactions between the manganese(III) ions in both compounds

An Oxide-Centered Trinuclear Manganese(III) Compound with a Bulky Phenol-Pyrazolate Ligand

A new oxide-centered trinuclear manganese(III) compound with the formula [Mn3(μ3-O)(naphpz)3(O2CMe)(MeOH)2]n (1) {H2naphpz = 2-[1H-pyrazol-5(3)-yl]naphthalen-1-ol} has been synthesized and characterized. Three bulky doubly deprotonated phenol-pyrazole ligands are coordinated to the three manganese(III) ions with a μ3-oxide bridge in the same plane. Methanol and acetate ligands are at the apical positions of the manganese(III) ions. The trinuclear units are bridged by acetate ligands in the anti-anti mode, leading to the formation of 1-D chains. Temperature-dependent magnetic susceptibility studies indicate the presence of overall antiferromagnetic interactions with magnetic exchange constants of J1 ≈ –1.9 and J2 ≈ –5.5 cm–1 and g = 1.91. Weak antiferromagnetic interactions (zJ′ = –0.37 cm–1) between the trinuclear units in the 1-D chain (and between the chains) in compound 1 are present.This work was financially supported by the EC-RTN “QuEMolNa” (No. MRTN-CT-2003-504880) and the ECNetwork of Excellence “MAGMANet” (No. 515767-2).Peer Reviewe

Metal-Organic Frameworks as Chemical Nanoreactors: Synthesis and Stabilization of Catalytically Active Metal Species in Confined Spaces

ConspectusSince the advent of the first metal-organic frameworks (MOFs), we have witnessed an explosion of captivating architectures with exciting physicochemical properties and applications in a wide range of fields. This, in part, can be understood under the light of their rich host-guest chemistry and the possibility to use single-crystal X-ray diffraction (SC-XRD) as a basic characterization tool. Moreover, chemistry on preformed MOFs, applying recent developments in template-directed synthesis and postsynthetic methodologies (PSMs), has shown to be a powerful synthetic tool to (i) tailor MOFs channels of known topology via single-crystal to single-crystal (SC-SC) processes, (ii) impart higher degrees of complexity and heterogeneity within them, and most importantly, (iii) improve their capabilities toward applications with respect to the parent MOFs. However, the unique properties of MOFs have been, somehow, limited and underestimated. This is clearly reflected on the use of MOFs as chemical nanoreactors, which has been barely uncovered. In this Account, we bring together our recent advances on the construction of MOFs with appealing properties to act as chemical nanoreactors and be used to synthesize and stabilize, within their channels, catalytically active species that otherwise could be hardly accessible. First, through two relevant examples, we present the potential of the metalloligand approach to build highly robust and crystalline oxamato- and oxamidato-MOFs with tailored channels, in terms of size, charge and functionality. These are initial requisites to have a playground where we can develop and fully take advantage of singular properties of MOFs as well as visualize/understand the processes that take place within MOFs pores and somehow make structure-functionalities correlations and develop more performant MOFs nanoreactors. Then, we describe how to exploit the unique and singular features that offer each of these MOFs confined space for (i) the incorporation and stabilization of metals salts and complexes, (ii) the in situ stepwise synthesis of subnanometric metal clusters (SNMCs), and (iii) the confined-space self-assembly of supramolecular coordination complexes (SCCs), by means of PSMs and underpinned by SC-XRD. The strategy outlined here has led to unique rewards such as the highly challenging gram-scale preparation of stable and well-defined ligand-free SNMCs, exhibiting outstanding catalytic activities, and the preparation of unique SCCs, different to those assembled in solution, with enhanced stabilities, catalytic activities, recyclabilities, and selectivities. The results presented in this Accounts are just a few recent examples, but highly encouraging, of the large potential way of MOFs acting as chemical nanoreactors. More work is needed to found the boundaries and fully understand the chemistry in the confined space. In this sense, mastering the synthetic chemistry of discrete organic molecules and inorganic complexes has basically changed our way of live. Thus, achieving the same degree of control on extended hybrid networks will open new frontiers of knowledge with unforeseen possibilities. We aim to stimulate the interest of researchers working in broadly different fields to fully unleash the host-guest chemistry in MOFs as chemical nanoreactors with exclusive functional species.This work was supported by the MINECO (Spain) (ProjectsCTQ2016-75671-P, 2017-86735-P, and Excellence Units“Severo Ochoa”and“Maria de Maeztu”SEV-2016-0683 andMDM-2015-0538) and the Ministero dell’Istruzione, dell’Uni-versitàe della Ricerca (Italy). Thanks are also extended to the“2019 Post-Doctoral Junior Leader-Retaining Fellowship, laCaixa Foundation (ID100010434 and Fellowship Code LCF/BQ/PR19/11700011”(J. F.-S.) and the Diamond LightSource for awarded beamtime and provision of synchrotronradiation facility at I19 beamline (D. A.). E.P. acknowledges thefinancial support of the European Research Council underthe European Union’s Horizon 2020 Research and InnovationProgramme/ERC Grant Agreement No. 814804, MOF-reactors

Oxidative double dehalogenation of tetrachlorocatechol by a bio-inspired Cu II complex: formation of chloranilic acid

Copper(II) complexes of the potentially tripodal N,N,O ligand 3,3-bis(1-methylimidazol-2-yl)propionate (L1) and its conjugate acid HL1 have been synthesised and structurally and spectroscopically characterised. The reaction of equimolar amounts of ligand and CuII resulted in the complexes [Cu(L1)]n(X)n (X=OTf-, PF6-; n=1,2), for which a new bridging coordination mode of L1 is inferred. Although these complexes showed moderate catecholase activity in the oxidation of 3,5-di-tert-butylcatechol, surprising reactivity with the pseudo-substrate tetrachlorocatechol was observed. A chloranilato-bridged dinuclear CuII complex was isolated from the reaction of [Cu(L1)]n(PF6)n with tetrachlorocatechol. This stoichiometric oxidative double dehalogenation of tetrachlorocatechol to chloranilic acid by a biomimetic copper(II) complex is unprecedented. The crystal structure of the product, [Cu2(ca)Cl2(HL1)2], shows a bridging bis-bidentate chloranilato (ca) ligand and ligand L1 coordinated as its conjugate acid (HL1) in a tridentate fashion. Magnetic susceptibility studies revealed weak antiferromagnetic coupling (J=-35 cm-1) between the two copper centres in the dinuclear complex. Dissolution of the green complex [Cu2(ca)Cl2(HL1)2] resulted in the formation of new pink-purple mononuclear compound [Cu(ca)(HL1)(H2O)], the crystal structure of which was determined. It showed a terminal bidentate chloranilato ligand and N,N-bidentate coordination of ligand HL1, which illustrates the flexible coordination chemistry of ligand L1