Direct Evidence of a Photoinduced Electron Transfer in Diluted “Molybdenum‐Copper” Molecular Compounds

Syntheses, Structures, and Magnetic Properties of Three Cyano-Bridged FeII-MoIII Single-Molecule Magnets

Three new cyano-bridged FeII-MoIII complexes assembled from the [MoIII(CN)7]4- unit, FeII ions, and three pentadentate N3O2 ligands, namely {[Fe2H3(dapab)2][Mo(CN)6]}n·2H2O·3.5MeCN (1), [Fe(H2dapb)(H2O)][Fe(Hdapb)(H2O)][Mo(CN)6]·4H2O·3MeCN (2), and [Fe(H2dapba)(H2O)]2[Mo(CN)7]·6H2O (3) (H2dapab = 2,6-diacetylpyridine bis(2-aminobenzoylhydrazone), H2dapb = 2,6-diacetylpyridine bis(benzoylhydrazone), H2dapba = 2,6-diacetylpyridine bis(4-aminobenzoylhydrazone)), have been synthesized and characterized. Single-crystal structure analyses suggest that complex 1 contains a one-dimensional (1D) chain structure where two FeII ions are bridged by the in situ generated [MoIII(CN)6]3- unit through two trans-cyanide groups into trinuclear Fe2IIMoIII clusters that are further linked by the amino of the ligand into an infinite chain. Complexes 2 and 3 are cyano-bridged Fe2IIMoIII trinuclear clusters with two FeII ions connected by the [MoIII(CN)6]3- and [MoIII(CN)7]4- units, respectively. Direct current magnetic studies confirmed the ferromagnetic interactions between the cyano-bridged FeII and MoIII centers and significant easy-axis magnetic anisotropy for all three complexes. Furthermore, complexes 1-3 exhibit slow magnetic relaxation under a zero dc field, with relaxation barriers of 42.3, 21.6, and 14.4 K, respectively, making them the first examples of cyano-bridged FeII-MoIII single-molecule magnets.

Influence of proton irradiation on the magnetic properties of two-dimensional Ni(II) molecular magnet

The influence of 1.9 MeV proton irradiation on structural and magnetic properties has been explored in the two-dimensional (2D) NiSO4(1,3-phenylenediamine)2 coordination ferrimagnet. The X-ray powder diffraction and IR spectroscopy revealed that the octahedrons with Ni ion in the center remain unchanged regardless of the fluence a sample received. In contrast, proton irradiation greatly influences the hydrogen bonds in the flexible parts in which the 1,3-phenylenediamine is involved. Dc magnetic measurements revealed that several magnetic properties were modified with proton irradiation. The isothermal magnetization measured at T = 2.0 K varied with the proton dose, achieving a 50% increase in magnetization in the highest measured field µ0Hdc = 7 T or a 25% decrease in remanence. The most significant change was observed for the coercive field, which was reduced by 90% compared to the non-irradiated sample. The observed results are accounted for the increased freedom of magnetic moments rotation and the modification of intralayer exchange couplings.

Experimental and theoretical insights into the photomagnetic effects in trinuclear and ionic Cu(ii)–Mo(iv) systems

New ionic and trinuclear copper(ii)–octacyanidomolybdate(iv) systems were developed and tested experimentally and theoretically to improve understanding of the photomagnetic effects.

Octacyanidometallates for multifunctional molecule-based materials

Octacyanidometallates have been successfully employed in the design of heterometallic coordination systems offering a spectacular range of desired physical properties with great potential for technological applications. The [M(CN)8]n- ions comprise a series of complexes of heavy transition metals in high oxidation states, including NbIV, MoIV/V, WIV/V, and ReV. Since the discovery of the pioneering bimetallic {MnII4[MIV(CN)8]2} and {MnII9[MV(CN)8]6} (M = Mo, W) molecules in 2000, octacyanidometallates were fruitfully explored as precursors for the construction of diverse d-d or d-f coordination clusters and frameworks which could be obtained in the crystalline form under mild synthetic conditions. The primary interest in [M(CN)8]n--based networks was focused on their application as molecule-based magnets exhibiting long-range magnetic ordering resulting from the efficient intermetallic exchange coupling mediated by cyanido bridges. However, in the last few years, octacyanidometallate-based materials proved to offer varied and remarkable functionalities, becoming efficient building blocks for the construction of molecular nanomagnets, magnetic coolers, spin transition materials, photomagnets, solvato-magnetic materials, including molecular magnetic sponges, luminescent magnets, chiral magnets and photomagnets, SHG-active magnetic materials, pyro- and ferroelectrics, ionic conductors as well as electrochemical containers. Some of these materials can be processed into the nanoscale opening the route towards the development of magnetic, optical and electronic devices. In this review, we summarise all important achievements in the field of octacyanidometallate-based functional materials, with the particular attention to the most recent advances, and present a thorough discussion on non-trivial structural and electronic features of [M(CN)8]n- ions, which are purposefully explored to introduce desired physical properties and their combinations towards advanced multifunctional materials.

Heterotrimetallic Cyanide-Bridged 3d-4d-5d Frameworks Based on a Photomagnetic Secondary Building Unit

The rational design of coordination frameworks combining more than two different metal ions using a self-assembly approach is challenging because it rarely offers sufficient control over the building blocks at the actual self-assembly stage. In this work, we present a successful two-step strategy toward heterotrimetallic coordination frameworks by employing a new bimetallic [(NC)₇Mo^IV-CN-Pt^IV(NH₃)₄-NC-Mo^IV(CN)₇]^4– secondary building unit (SBU). This anionic moiety has been isolated and characterized as a simple salt with an organic dppipH₂²⁺ cation (dppipH₂)₂[(NC)₇Mo^IV-CN-Pt^IV(NH₃)₄-NC-Mo^IV(CN)₇]·15H₂O (1) (dppip = 1,4-di(4-pyridinyl)piperazine). The salt presents a second-order phase transition related to cation conformational change around 250 K and a photomagnetic effect after irradiation with 450 nm light at 10 K. When combined with aqueous solutions of Mn^II or Cu^II complexes, it forms either a one-dimensional chain [Mn^II(dpop)][Mn^II(dpop)(H₂O)][(NC)₇Mo^IV-CN-Pt^IV(NH₃)₄-NC-Mo^IV(CN)₇]·36H₂O (2) (dpop = 2,13-dimethyl-3,6,9,12,18-pentaazabicyclo-[12.3.1]octadeca-1(18),2,12,14,16-pentaene) or a photomagnetic two-dimensional honeycomb network [Cu^II(cyclam)]₂[(NC)₇Mo^IV-CN-Pt^IV(NH₃)₄-NC-Mo^IV(CN)₇]·40.89H₂O (3) (cyclam = 1,4,8,11-tetraazacyclotetradecane), both characterized by very large cavities in their structure filled with solvent molecules. Both 2 and 3 incorporate three different transition-metal ions and constitute a new family of 3d-4d-5d coordination frameworks. Moreover, compound 3 inherits the photomagnetic properties of the MoPtMo SBU.

A photomagnetic secondary building unit (SBU) Mo^IVPt^IVMo^IV was employed to design and synthesize new heterotrimetallic coordination polymers in a two-step approach, resulting in Mn^II₂Mo^IV₂Pt^IV coordination chains and Cu^II₂Mo^IV₂Pt^IV honeycomb coordination layers.

The photomagnetic effect in 2-D cyanido-bridged coordination polymer [Cu(aepa)]10[Mo(CN)8]5·30H2O

The 2-D [Cu(aepa)]₁₀[Mo(CN)₈]₅·30H₂O (aepa = N-(2-aminoethyl)-1,3-propanediamine) coordination network exhibits a photomagnetic effect due to singlet–triplet transition on the Mo(iv) centre accompanied by metal–metal charge transfer.