Yuting Chen

Hydrogen-Bond Directed Cyanide-Bridged Molecular Magnets Derived from Polycyanidemetalates and Schiff Base Manganese(III) Compounds: Synthesis, Structures, and Magnetic Properties

A series of six new cyanide-bridged heterometallic complexes including two tetranuclear T-like Fe(III)Mn(III)(3) compounds, {[Mn(L(1))(H(2)O)](3)[Fe(CN)(5)(1-CH(3)im)]}ClO(4) x 1.5 H(2)O (1) and {[Mn(L(2))(H(2)O)](3)[Fe(CN)(5)(1-CH(3)im)]}ClO(4) x 3 H(2)O (2); two heptanuclear cage-shaped M(III)Mn(III)(6) (M = Fe, Cr) compounds, {[Mn(L(2))(H(2)O)](6)[Fe(CN)(6)]}[Fe(CN)(6)] x 6 CH(3)OH (3) and {[Mn(L(2))(H(2)O)](6)[Cr(CN)(6)]}[Cr(CN)(6)] x 6 CH(3)OH (4); and two two-dimensional M-Mn(III) networks, {[H(3)O][Mn(L(1))](2)[Fe(CN)(6)]} x 2 DMF (5) and {K[Mn(L(1))](2)[Cr(CN)(6)]} x 1.5 CH(3)CN x CH(3)OH (6) (L(1) = N,N-ethylene-bis(3-methoxysalicylideneiminate, L(2) = N,N-ethylene-bis(3-ethoxysalicylideneiminate) have been successfully assembled from three polycyanidemetalates containing five or six cyanide groups and two manganese(III) building blocks containing bicompartmental Schiff base ligands. The cyanide-bridged polynuclear complexes are self-complementary through a coordinated aqua ligand from one complex and the free O(4) compartment from the neighboring complex, giving supramolecular one-dimensional ladders and three-dimensional networks for 1 and 2 and for 3 and 4, respectively. Investigation over magnetic susceptibilities of the six complexes reveals the overall ferromagnetic interactions for complexes 1, 2, 3, and 5 and antiferromagnetic interaction for 4 and 6. Compounds 1-4 show some characteristics of metamagnet behavior at low temperatures due to the relatively strong intermolecular hydrogen-bonding interaction. The two complexes with two-dimensional structure exhibit three-dimensional antiferromagnetic ordering with typical metamagnetic behavior below 8.4 K for 5 and 11.5 K for 6, respectively. The present result appears to add new members to the very few examples of polynuclear clusters exhibiting 3D magnetic ordering relying on intermolecular interactions, to the best of our knowledge, which will be helpful for providing valuable information for the understanding and application of intermolecular hydrogen-bonding interactions in the molecular magnetic materials.

8-Hydroxyquinoline-substituted boron-dipyrromethene compounds: synthesis, structure, and OFF-ON-OFF type of pH-sensing properties.

A series of four novel 8-hydroxyquinoline-substituted boron-dipyrromethene derivatives, namely 4,4-difluoro-8-(5-(8-hydroxyquinoline))-3,5-dimethyl-4-bora-3a,4a-diaza-s-indacene (1), 4,4-difluoro-8-(5-(8-hydroxyquinoline))-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene (2), 4,4-difluoro-8-(5-azastyryl-(8-hydroxyquinoline))-3,5-dimethyl-4-bora-3a,4a-diaza-s-indacene (3), and 4,4-difluoro-8-(5-azastyryl-(8-hydroxyquinoline))-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene (4), have been synthesized and characterized by a series of spectroscopic methods. The molecular structures of 1 and 2 have been determined by single-crystal X-ray diffraction analyses. The two methyl substituents attached at C-1 and C-7 positions of boron-dipyrromethene (Bodipy) in compound 2 was revealed to prevent the free rotation of the 8-hydroxyquinoline (8-HQ) moiety, resulting in an almost vertical 8-HQ-Bodipy configuration of this compound. This is obviously different from those for 1 with the dihedral angle between 8-hydroxyquinoline and Bodipy moieties of 65.44 and 66.79° due to the lack of methyl substituents in the latter compound. The intense fluorescence from the Bodipy subunit of these compounds was revealed to gradually get diminished along with either decreasing or increasing the pH value under acidic and basic conditions, respectively, in particular for 1, 2, and 4 because of the photoinduced intramolecular electron transfer from excited Bodipy moiety to 8-HQ unit and just an opposite process. This renders these compounds the first OFF-ON-OFF type of pH-dependent fluorescent sensors. Nevertheless, both the intrinsic fluorescence of these compounds and their fluorescent quenching properties along with the change in the pH value have been found to depend on the steric configuration as well as the linking group between 8-hydroxyquinoline and Bodipy moieties, revealing the effect of molecular structure on their fluorescence properties.

Diverse Ni(II) MOFs constructed from asymmetric semi-rigid V-shaped multicarboxylate ligands: structures and magnetic properties

Novel nickel(II) coordination polymers have been constructed from asymmetric semi-rigid V-shaped multicarboxylate ligands with the help of 4,4′-bipyridine (4,4′-bpy) ligand. The hydrothermal reaction between 3-(4-carboxy-phenoxy)-phthalic acid (H3L1) and Ni(OAc)2·4H2O led to the formation of [Ni3(L1)2(μ-4,4′-bpy)3(H2O)2]n·(4,4′-bpy)n·(H2O)5n (1). In contrast, the same reaction using 3-(2-carboxy-phenoxy)-phthalic acid (H3L2) as a starting material instead of H3L1 resulted in [Ni3(L2)2(H2O)4(μ-4,4′-bpy)3]n·(H2O)2n (2) and [Ni3(L2)2(H2O)4(μ-4,4′-bpy)4]n·(H2O)2n (3) at 120 and 150 °C, respectively, revealing the effect of reaction temperature on the structure of the coordination polymer formed from the semi-rigid V-shaped ligand of L2. Single-crystal X-ray diffraction analysis reveals that complex 1 shows a 3D framework structure assembled from right- and left-handed helices together with isolated tubes. This compound represents the first metal–organic hybrid tube constructed from an asymmetric semi-rigid V-shaped multicarboxylate ligand. Compound 2 also exhibits a 3D network composed of discontiguous trinuclear Ni(II) clusters, while the 3D architecture of 3 consisting of isolated Ni(II) ions separated in a long distance is constructed by two kinds of 2D (6,3) networks. Magnetic studies reveal the overall antiferromagnetic interaction between the neighbouring Ni(II) ions in 1–3.

Heterobimetallic porphyrin-based single-chain magnet constructed from manganese(III)-porphyrin and trans-dicyanobis(acetylacetonato) ruthenate(III) containing co-crystallized bulk anions and cations

Two cyanide-bridged alternated 1 : 1 Ru(III)/Mn(III) complexes structurally characterized as single-chain containing co-crystallized bulk anions and cations have been successfully assembled from [Mn(TPP)(H(2)O)(2)](+) and [Ru(acac)(2)(CN)(2)](-) blocks. Systematic investigation of their magnetic properties reveals typical single-chain magnet (SCM) behaviors for both of them.

Rational design and synthesis for versatile FRET ratiometric sensor for Hg2+ and Fe2+: a flexible 8-hydroxyquinoline benzoate linked Bodipy-porphyrin dyad.

A flexible 8-hydroxyquinoline benzoate linked Bodipy-porphyrin dyad has been designed, synthesized, and characterized. Binding of this dyad with Hg(2+)/Fe(2+) induced just the opposite (promoting/restraining) influence on energy transfer from the Bodipy donor to the porphyrin acceptor, resulting in a remarkably different ratio change of two signal emissions, endowing this dyad as the first Bodipy-porphyrin-based versatile fluorescence resonance energy transfer (FRET) ratiometric sensor for Hg(2+) and Fe(2+) ions, respectively.

Modulation of the spectroscopic property of Bodipy derivates through tuning the molecular configuration

A series of six Bodipy derivatives, namely 4,4-difluoro-8-(4-amidophenyl)-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene (1), 4,4-difluoro-8-(4-methylphenyl)-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene (2), 4,4-difluoro-8-(4-nitrylphenyl)-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene (3), 4,4-difluoro-8-(4-amidophenyl)-3,5-dimethyl-4-bora-3a,4a-diaza-s-indacene (4), 4,4-difluoro-8-(4-methylphenyl)-3,5-dimethyl-4-bora-3a,4a-diaza-s-indacene (5), and 4,4-difluoro-8-(4-nitrylphenyl)-3,5-dimethyl-4-bora-3a,4a-diaza-s-indacene (6) were structurally characterized by single crystal X-ray diffraction analysis. Two methyl substituents attached at C-1 and C-7 positions of boron-dipyrromethene (Bodipy) moiety in compounds 1-3 were revealed to prevent the free rotation of the benzene moiety, resulting in a molecular configuration with an almost orthogonal dihedral angle between the Bodipy and benzene moieties with the dihedral angle in the range of 81.14-88.56°. This is obviously different from that for 4-6 with a free-rotating benzene moiety relative to the Bodipy core due to the lack of two methyl substituents in the latter series of compounds, leading to an enhanced interaction between the Bodipy and benzene moieties for 4-6 in comparison with 1-3. The resulting larger HOMO-LUMO gap for 1-3 than 4-6 results in a blue-shifted absorption band for 1-3 relative to that for 4-6. Comparative studies over their fluorescence properties also disclose the blue-shifted fluorescence emission band and corresponding higher fluorescence quantum yield for 1-3 relative to those of 4-6, revealing the effect of molecular configuration on the spectroscopic properties of Bodipy derivatives. Comparison of the redox behaviors of these two series of Bodipy compounds provides additional support for this point. In addition, the electron-donating/withdrawing property of the para substituent of the benzene moiety was shown to exhibit a slight influence on the electronic absorption and fluorescence emission properties of the Bodipy compounds.