Self-Assembly of a Redox Active,Metallosupramolecular [Pd3L6]6+ Complex Using a Rotationally Flexible Ferrocene Ligand

A new ferrocene-containing [Pd₃( L_4EFc )₆]⁶⁺(X⁻)₆ ( C ⋅ BF₄ and C ⋅ SbF₆ where X=BF₄⁻ or SbF₆⁻) self-assembled double-walled triangle has been synthesized from the known, rotationally flexible, 1,1′-bis(4-pyridylethynyl)ferrocene ligand ( L_4EFc ), and characterized by ¹H, ¹³C and diffusion ordered (DOSY) NMR spectroscopies, high-resolution electrospray ionization mass spectrometry (HR−ESI−MS), X-ray crystallography and cyclic voltammetry (CV). The molecular structures confirmed that double-walled triangle cage systems ( C ⋅ BF₄ and C ⋅ SbF₆ ) were generated. C ⋅ BF₄ was shown to interact with the anionic guest, p-toluenesulfonate. CV experiments revealed that the triangles were redox active, however addition of the guest did not influence the redox potentials.     

Organosulfonate-Modulated Spin-Crossover Behavior in Three Halogen-Functionalized Cobalt(II) Complexes

We present here the syntheses, crystal structures, and spin crossover (SCO) properties of a series of halogen-functionalized cobalt(II) complexes, [Co(Brphtpy)₂](OTf)₂ ⋅ DMF ⋅ 2H₂O ( 1 ), [Co(Brphtpy)₂](HBS)₂ ⋅ H₂O ( 2 ), [Co(Brphtpy)₂](MQ)₂ ⋅ 2MeCN ⋅ 3H₂O ( 3 ) ( Brphtpy =4′–(4-Bromophenyl)–2,2′:6′,2′′-terpyridine; OTf⁻=trifluoromethanesulfonate; HBS⁻=hydroxybenzenesulfonate dihydrate; MQ⁻=methyl orange). Variable-temperature single-crystal X-ray analyses revealed mononuclear compounds of 1 – 3 consisted of [Co(Brphtpy)₂]²⁺ SCO active units and organosulfonate anions and no structural phase transformation happened in measured high-low temperature. The packing structures of these complexes were tuned by varying organosulfonates. However, no notable supramolecular interactions can be found, in turn leading to gradual, incomplete, and non-hysteretic SCO behaviors. Interestingly, the SCO behaviors of these three complexes were significantly modified after the removal of lattice solvents. Combined structural and magnetic investigations revealed the non-cooperative supramolecular packing structures, guest internal pressure, and the small structural distortions of the SCO units should be responsible for the worse SCO properties of 1 – 3 . The foregoing results show that to achieve high-performance Co²⁺ SCO, both the weak interactions, internal pressure, and structural distortion should be considered during the design and construction of SCO complexes.     

Effect of Axial Ligands on Easy-Axis Anisotropy and Field-Induced Slow Magnetic Relaxation in Heptacoordinated FeII Complexes

A rational approach to modulating easy-axis magnetic anisotropy by varying the axial donor ligand in heptacoordinated Fe^II complexes has been explored. In this series of complexes with formulae of [Fe(H₄L)(NCS)₂] ⋅ 3 DMF ⋅ 0.5 H₂O ( 1 ), [Fe(H₄L)(NCSe)₂] ⋅ 3 DMF ⋅ 0.5 H₂O ( 2 ), and [Fe(H₄L)(NCNCN)₂] ⋅ DMF ⋅ H₂O ( 3 ) [H₄L=2,2′-{pyridine-2,6-diylbis(ethan-1-yl-1-ylidene)}bis(N-phenylhydrazinecarboxamide)], the axial positions are successively occupied by different nitrogen-based π-donor ligands. Detailed dc and ac magnetic susceptibility measurements reveal the existence of easy-axis magnetic anisotropy for all of the complexes, with 1 [U_eff=21 K, τ₀=1.72×10⁻⁶ s] and 2 [U_eff=25 K, τ₀=2.25×10⁻⁶ s] showing field-induced slow magnetic relaxation behavior. However, both experimental studies and theoretical calculations indicate the magnitude of the D value of complex 3 to be larger than those of complexes 1 and 2 due to the axial bond angle being smaller than that for an ideal geometry. Detailed analysis of the field and temperature dependences of relaxation time for 1 and 2 has revealed that multiple relaxation processes (quantum tunneling of magnetization, direct, and Raman) are involved in slow magnetic relaxation for both of these complexes. Magnetic dilution experiments support the role of intermolecular short contacts.     

Exceptional Substrate Diversity in Oxygenation Reactions Catalyzed by a Bis(μ-oxo) Copper Complex

The enzyme tyrosinase contains a reactive side-on peroxo dicopper(II) center as catalytically active species in C−H oxygenation reactions. The tyrosinase activity of the isomeric bis(μ-oxo) dicopper(III) form has been discussed controversially. The synthesis of bis(μ-oxo) dicopper(III) species [Cu₂(μ-O)₂( L1 )₂](X)₂ ([ O1 ](X)₂, X=PF₆⁻_, BF₄⁻, OTf⁻, ClO₄⁻), stabilized by the new hybrid guanidine ligand 2-{2-((dimethylamino)methyl)phenyl}-1,1,3,3-tetramethylguanidine ( L1 ), and its characterization by UV/Vis, Raman, and XAS spectroscopy, as well as cryo-UHR-ESI mass spectrometry, is described. We highlight selective oxygenation of a plethora of phenolic substrates mediated by [ O1 ](PF₆)₂, which results in mono- and bicyclic quinones and provides an attractive strategy for designing new phenazines. The selectivity is predicted by using the Fukui function, which is hereby introduced into tyrosinase model chemistry. Our bioinspired catalysis harnesses molecular dioxygen for organic transformations and achieves a substrate diversity reaching far beyond the scope of the enzyme.     

Partial Molar Volumes and Partial Molar Adiabatic Compressibilities of Fe(III) Tetrafluoroborate Complexes with DMSO, Pyridine, and Pyridine Derivatives

The apparent and limiting apparent molar volumes of dilute aqueous solutions of KBF₄, and the complexes [Fe(DMSO)₆](BF₄)₃, [Fe(Py)₄(H₂O)₂](BF₄)₃, [Fe(4-Mepy)₂(H₂O)₂](BF₄)₃, and [Fe(4-Etpy)₂(H₂O)₂](BF₄)₃ were determined from density data measured at 5, 15, and 25°C. The apparent and limiting apparent molar adiabatic compressibilities of these complexes were determined from ultrasonic sound velocities measured at the same temperatures in dilute aqueous solutions. The volume change associated with complex formation is discussed in terms of the nature of the coordinate bond and also the role of the central metal atom and ligands in the solvation behavior of these complexes.     

Solid state thermal isomerisation of diethylenetriamine complexes of NiX2 (X=NO3, ClO4, BF4 and CF3SO3)

Summary [Ni(dien)₂]X₂·nH₂O (dien=diethylenetriamine; n=0, X=NO₃ or CF₃SO₃; n=0.5, X=ClO₄ or BF₄ and n=2, X=CF₃SO₃) complexes have been prepared and investigated thermally in the solid state. [Ni(dien)₂](NO₃)₂ (1) and [Ni(dien)₂](CF₃SO₃)₂ (2) undergo endothermic irreversible phase transitions (209–247°C and 184–205°C; H=5.6 kJ mol^–1 and 7.7 kJ mol^–1 for (1) and (2), respectively). [Ni(dien)₂](ClO₄)₂·0.5H₂O (3) shows an endothermic irreversible phase transition after deaquation (201–216°C; H=7.7 kJ mol^–1). [Ni(dien)₂](BF₄)₂·0.5H₂O also shows an endothermic irreversible phase transition after deaquation, accompanied by partial decomposition. All the complexes possess octahedral geometry with the ligands arranged meridionally. The phase transitions are explained in terms of conformational changes of the triamine chelate rings.Author to whom all correspondence should be directed. Supplementary data available: i.r. spectra (Table 4) and x-ray diffraction patterns (Table 5).     

Synthesis and study of cobalt(II), nickel(II), and copper(II) complexes with 4-(4-hydroxyphenyl)-1,2,4-triazole

New complexes of Co(II), Ni(II), and Cu(II) nitrates, chlorides, and perchlorates with 4-(4-hydroxyphenyl)-1,2,4-triazole (L) were obtained and examined by single-crystal X-ray diffraction, X-ray powder diffraction, and electronic absorption and IR spectroscopy. The cations of all the complexes have linear trinuclear structures. Ligand L is coordinated to the metal ions in a bidentate bridging fashion through the N(1) and N(2) atoms of the heterocycle. The coordination polyhedron of the metal atoms is a distorted octahedron. The molecular and crystal structures of the complexes [Co₃L₆(H₂O)₆](ClO₄)₆ · 3C₂H₅OH · 3.75H₂O and [M₃L₆(H₂O)₆](ClO₄)₆ · 6H₂O (M = Cu²⁺ and Ni²⁺) were determined.     

Spin-Crossover Iron(II) Compounds with Pendent Tetraphenylethylene Group

Two iron(II) compounds with the general formula of [Fe(phen-TPE)₂(NCX)₂] ⋅ Y (phen-TPE=3-(tetraphenylethylene)-1,10-phenanthroline; X=S and Y=2DMF for 1 ⋅ 2DMF ; X=Se and Y=DMF for 2 ⋅ DMF ) were synthesized and characterized by single-crystal X-ray crystallography and magnetic measurements. Both compounds exhibited thermal-induced complete one-step spin-crossover (SCO) behavior with the critical transition temperatures of 210 K and 260 K for 1 ⋅ 2DMF and 2 ⋅ DMF , respectively. The SCO behavior of these two isomorphic compounds depended significantly on robust intermolecular π⋅⋅⋅π interactions, NCX⁻ groups and solvent molecules.     

Trapping an Unexpected/Unprecedented Hexanuclear Ce(III) Hydrolysis Product with Neutral 4-Amino-1,2,4-triazole

Using Ce(III) as both a representative lanthanide and actinide analog, the ability of mixtures of acidic and basic azoles to allow direct access to homoleptic N-donor f-element complexes in one pot reactions from hydrated salts as starting materials was examined by reacting mixtures of 4-amino-1,2,4-triazole (4-NH₂-1,2,4-Triaz), 5-amino-tetrazole (5-NH₂-HTetaz), and 1,2,3-triazole (1,2,3-HTriaz) in 1 : 1 and 1 : 3 ratios with CeCl₃ ⋅ 7H₂O, [C₂mim]₃[CeCl₆] ([C₂mim]⁺=1-ethyl-2-methylimidazolium), and Ce(NO₃)₃ ⋅ 6H₂O. Although unsuccessful in our goal, structural analysis revealed that neutral 4-NH₂-1,2,4-Triaz is structure directing via η²μ₂κ² bridging, with the formation of the dinuclear complexes [Ce₂Cl₂(μ₂-4-NH₂-1,2,4-Triaz)₄(H₂O)₈]Cl₄ ⋅ 4H₂O, [Ce₂(μ₂-4-NH₂-1,2,4-Triaz)₄(4-NH₂-1,2,4-Triaz)₂(Cl)₆], and [4-NH₂-1,2,4-HTriaz][Ce₂(μ₂-4-NH₂-1,2,4-Triaz)₂(μ₂-NO₃)(NO₃)₆(H₂O)₂]. When the synthetic conditions favored hydrolysis, the hexanuclear Ce(III) complex [Ce₆(μ₃-O)₄(μ₃-OH)₂(μ₃-Cl)₂(Cl)₆(μ₂-4-NH₂-1,2,4-Triaz)₁₂] ⋅ 7H₂O was isolated. This unexpected hydrolysis product represents the first example of a high nuclearity lanthanide complex where all Ln atoms are pairwise connected through 12 N-donor ligands or 12 neutral bridging ligands of any type, a rare example of incorporation of non-oxo coordinating anions in the M₆X₈ core, and the first reported Ce(III) hexanuclear complex of this type.     

Two‐Step Spin Transition in a 1D FeII 1,2,4‐Triazole Chain Compound

A thermochromic 1D spin crossover coordination (SCO) polymer [Fe(βAlatrz)₃](BF₄)₂ ? 2 H₂O ( 1? 2 H₂O), whose precursor βAlatrz, (1,2,4‐triazol‐4‐yl‐propionate) has been tailored from a β‐amino acid ester is investigated in detail by a set of superconducting quantum interference device (SQUID), ⁵⁷Fe Mössbauer, differential scanning calorimetry, infrared, and Raman measurements. An hysteretic abrupt two‐step spin crossover (T_1/2^↓=230 K and T_1/2^↑=235 K, and T_1/2^↓=172 K and T_1/2^↑=188 K, respectively) is registered for the first time for a 1,2,4‐triazole‐based Fe^II 1D coordination polymer. The two‐step SCO configuration is observed in a 1:2 ratio of low‐spin/high‐spin in the intermediate phase for a 1D chain. The origin of the stepwise transition was attributed to a distribution of chains of different lengths in 1? 2 H₂O after First Order Reversal Curves (FORC) analyses. A detailed DFT analysis allowed us to propose the normal mode assignment of the Raman peaks in the low‐spin and high‐spin states of 1? 2 H₂O. Vibrational spectra of 1? 2 H₂O reveal that the BF₄^? anions and water molecules play no significant role on the vibrational properties of the [Fe(βAlatrz)₃]²⁺ polymeric chains, although non‐coordinated water molecules have a dramatic influence on the emergence of a step in the spin transition curve. The dehydrated material [Fe(βAlatrz)₃](BF₄)₂ ( 1 ) reveals indeed a significantly different magnetic behavior with a one‐step SCO which was also investigated.     

Iron(II) and Nickel(II) Complexes of N‐Alkylimidazoles and 1‐Methyl‐1H‐1, 2, 4‐Triazole: X‐ray Studies,Magnetic Characterization,and DFT Calculations

Using the ligands N‐methylimidazole ( MeIm ), N‐ethylimidazole ( EtIm ), N‐propylimidazole ( PrIm ), and 1‐methyl‐1H‐1, 2, 4‐triazole ( MeTz ) three series with a total of 13 iron(II) complexes were isolated. The series comprise of the following complexes: (a) [Fe( MeIm )₆](ClO₄)₂ ( 1 ), [Fe( EtIm )₆](ClO₄)₂ ( 2 ), [Fe( PrIm )₆](ClO₄)₂( 3 ), [Fe( MeTz )₆](ClO₄)₂ ( 4 ), [Fe( MeIm )₆](MeSO₃)₂ ( 5 ), [Fe( EtIm )₆](MeSO₃)₂ ( 6 ), and [Fe( MeTz )₆](BF₄)₂ ( 10 ); (b) [Fe( MeIm )₄(MeSO₃)₂]( 7 ), [Fe( EtIm )₄(MeSO₃)₂] ( 8 ), and [Fe( PrIm )₄(MeSO₃)₂] ( 9 ); (c) [Fe( MeIm )₄(NCS)₂] ( 15 ), [Fe( EtIm )₄(NCS)₂] ( 16 ), and [Fe( MeTz )₄(NCS)₂] ( 17 ). Single crystal X‐ray diffraction studies were performed on 7 – 10 and 15 – 17 . Temperature dependent magnetic susceptibility measurements were performed on selective examples of all series, and confirmed them to be in the HS state over the range 6–300 K. DFT calculations were performed at BP86/def‐SV(P) and TPSSh/def2‐TZVPP level on all [Fe L ₆]²⁺ complex cations and the neutral complexes 7 – 9 and 15 – 17 . Additionally the four homoleptic nickel(II) complexes [Ni L ₆](ClO₄)₂ ( 11 : L = MeIm ; 12 : L = EtIm ; 13 : L = PrIm ; 14 : L = MeTz ) were synthesized and compounds 11 – 13 structurally characterized. UV/Vis/NIR spectroscopic measurements were carried out on all homoleptic iron(II) and nickel(II) complexes. The 10Dq values were determined to be in the range of 11547–11574 and 10471–10834 cm^–1 for the iron(II) and nickel(II) complexes, respectively.     

Two linear trinuclear clusters with bridging triazole: crystal structure and magnetism

Two linear trinuclear clusters, [Co₃(L)₆(H₂O)₆](ClO₄)₆ (1) and [Ni₃(L)₆(H₂O)₆](ClO₄)₆?·?3H₂O (2) (L?=?4-(4-hydroxyphenyl)-1,2,4-triazole), obtained by the reactions of M(ClO₄)₂?·?6H₂O and 4-(4-hydroxyphenyl)-1,2,4-triazole have been isolated and structurally characterized. The two isostructural clusters, linear hexapositive trimers, are linked by three N1,N2-1,2,4-triazoles to the divalent central and terminal metal ions. The magnetic behaviors of the clusters were investigated from 1.8 to 300?K. Magnetic susceptibility measurements reveal antiferromagnetic exchange interactions between the metal centers in the clusters. The magnetic data were analyzed by using linear trinuclear modes with S?=?3/2 and S?=?1 for 1 and 2, respectively. Further studies were performed by accounting spin–orbital coupling for 1 and involving zero-field splitting within the ground state for 2.     

Three polynuclear complexes with bridging triazole ligand: crystal structures

Three polynuclear clusters, [Cu₄L₈](ClO₄)₄·4H₂O (1), [Zn₃L₆(H₂O)₆](ClO₄)₆·6H₂O (2), and [Mn₃L₆(CH₃OH)₆](ClO₄)₆·4.5H₂O (3) (L?=?4-(4-hydroxyphenyl)-1,2,4-triazole), obtained by the reactions of M(ClO₄)₂·6H₂O with L have been isolated and structurally characterized. Complex 1 featured a tetranuclear Cu(I) structure. Both 2 and 3 are linear hexapositive trimers linked by three N1,N2–1,2,4-triazole ligands to the divalent central and terminal metal ions. Furthermore, the luminescence properties of 2 were investigated at room temperature in the solid state.     

Further Evidence for ‘Extended’ Cumulene Complexes: Derivatives from Reactions with Halide Anions and Water

Reactions of [Ru{C=C(H)-1,4-C₆H₄C≡CH}(PPh₃)₂Cp]BF₄ ([ 1 a ]BF₄) with hydrohalic acids, HX, results in the formation of [Ru{C≡C-1,4-C₆H₄-C(X)=CH₂}(PPh₃)₂Cp] [X=Cl ( 2 a-Cl ), Br ( 2 a-Br )], arising from facile Markovnikov addition of halide anions to the putative quinoidal cumulene cation [Ru(=C=C=C₆H₄=C=CH₂)(PPh₃)₂Cp]⁺. Similarly, [M{C=C(H)-1,4-C₆H₄-C≡CH}(LL)Cp ]BF₄ [M(LL)Cp’=Ru(PPh₃)₂Cp ([ 1 a ]BF₄); Ru(dppe)Cp* ([ 1 b ]BF₄); Fe(dppe)Cp ([ 1 c ]BF₄); Fe(dppe)Cp* ([ 1 d ]BF₄)] react with H⁺/H₂O to give the acyl-functionalised phenylacetylide complexes [M{C≡C-1,4-C₆H₄-C(=O)CH₃}(LL)Cp’] ( 3 a – d ) after workup. The Markovnikov addition of the nucleophile to the remote alkyne in the cations [ 1 a–d ]⁺ is difficult to rationalise from the vinylidene form of the precursor and is much more satisfactorily explained from initial isomerisation to the quinoidal cumulene complexes [M(=C=C=C₆H₄=C=CH₂)(LL)Cp’]⁺ prior to attack at the more exposed, remote quaternary carbon. Thus, whilst representative acetylide complexes [Ru(C≡C-1,4-C₆H₄-C≡CH)(PPh₃)₂Cp] ( 4 a ) and [Ru(C≡C-1,4-C₆H₄-C≡CH)(dppe)Cp*] ( 4 b ) reacted with the relatively small electrophiles [CN]⁺ and [C₇H₇]⁺ at the β-carbon to give the expected vinylidene complexes, the bulky trityl ([CPh₃]⁺) electrophile reacted with [M(C≡C-1,4-C₆H₄-C≡CH)(LL)Cp’] [M(LL)Cp’=Ru(PPh₃)₂Cp ( 4 a ); Ru(dppe)Cp* ( 4 b ); Fe(dppe)Cp ( 4 c ); Fe(dppe)Cp* ( 4 d )] at the more exposed remote end of the carbon-rich ligand to give the putative quinoidal cumulene complexes [M{C=C=C₆H₄=C=C(H)CPh₃}(LL)Cp’]⁺, which were isolated as the water adducts [M{C≡C-1,4-C₆H₄-C(=O)CH₂CPh₃}(LL)Cp’] ( 6 a–d ). Evincing the scope of the formation of such extended cumulenes from ethynyl-substituted arylvinylene precursors, the rather reactive half-sandwich (5-ethynyl-2-thienyl)vinylidene complexes [M{C=C(H)-2,5-^cC₄H₂S-C≡CH}(LL)Cp’]BF₄ ([ 7 a – d ]BF₄ add water readily to give [M{C≡C-2,5-^cC₄H₂S-C(=O)CH₃}(LL)Cp’] ( 8 a – d )].     

Adducts of coordination compounds-XIII. Nitrates,hydrogen and silver dinitrates,and polysilver nitrates of trans-dihalotetrakispyridinerhodium(III) and iridium(III) ions

The synthesis and characterization, chiefly as salts of the anions [X(ONO₂)₂]⁻ (X = H⁺ or Ag⁺) (by analysis, X-ray powder photography, vibrational spectra and thermogravimetry) of adducts of the nitrates trans-[M(L)₄X₂](NO₃) (M =Rh or Ir; L = pyridine, perdeuteriopyridine or 4-methylpyridine; X = Cl or Br) with hydrogen nitrate and silver nitrate are described.     

Preparation, molecular structure, and thermal analyses of a novel coordination compound [Cd(AZT)4(H2O)2](PA)2 · 4H2O (AZT = 3-azido-1,2,4-triazole, PA = picrate)

Abstract  The crystal structure of 3-azido-1,2,4-triazole (AZT) has been determined. A novel coordination compound [Cd(AZT)₄(H₂O)₂](PA)₂ · 4H₂O has been synthesized by using 3-azido-1,2,4-triazole as ligand, and its structure has been characterized by using X-ray single crystal diffraction, elemental analysis, and FT-IR spectroscopy. Each cadmium (II) center is coordinated with four N atoms of four AZT molecules and two O atoms of two H₂O molecules to form a slightly distorted octahedron. The optimized molecular structure and NBO charges of 3-azido-1,2,4-triazole have been obtained from the density functional theory (DFT) with the B3LYP method employing the 6-311 + G** basis sets. Thermal decomposition mechanism of [Cd(AZT)₄(H₂O)₂](PA)₂ · 4H₂O has been predicted based on DSC, TG-DTG, and FT-IR analyses. The kinetic parameters of the first exothermic process of [Cd(AZT)₄(H₂O)₂](PA)₂ · 4H₂O were studied by applying the Kissinger’s and Ozawa-Doyle’s methods. Index Abstract  A novel coordination compound [Cd(AZT)₄(H₂O)₂](PA)₂ · 4H₂O has been synthesized by using 3-azido-1,2,4-triazole as ligand and its structure has been characterized by using X-ray single crystal diffraction, elemental analysis, and FT-IR spectroscopy. Each cadmium (II) center is coordinated to form a slightly distorted octahedron. Thermal decomposition mechanism of [Cd(AZT)₄(H₂O)₂](PA)₂ · 4H₂O has been predicted based on DSC, TG-DTG, and FT-IR analyses.      

Solvent-Vapor-Induced Reversible Single-Crystal-to-Single-Crystal Transformation of a Triphosphaazatriangulene-Based Metal–Organic Framework

A triphosphaazatriangulene (H₃L) was synthesized through an intramolecular triple phospha-Friedel–Crafts reaction. The H₃L triangulene contains three phosphinate groups and an extended π-conjugated framework, which enables the stimuli-responsive reversible transformation of [Cu(HL)(DMSO)⋅(MeOH)]_n, a 3D-MOF that exhibits reversible sorption characteristics, into (H₃L⋅0.5 [Cu₂(OH)₄⋅6 H₂O] ⋅4 H₂O), a 1D-columnar assembled proton-conducting material. The hydrophilic nature of the latter resulted in a proton conductivity of 5.5×10⁻³ S cm⁻¹ at 95 % relative humidity and 60 °C.     

Highly Stable Copper(I)–Thiacalix[4]arene-Based Frameworks for Highly Efficient Catalysis of Click Reactions in Water

Environmentally friendly metal–organic frameworks (MOFs) have gained considerable attention for their potential use as heterogeneous catalysts. Herein, two Cu^I-based MOFs, namely, [Cu₄Cl₄L] ⋅ CH₃OH ⋅ 1.5 H₂O ( 1-Cl ) and [Cu₄Br₄L] ⋅ DMF ⋅ 0.5 H₂O ( 1-Br ), were assembled with new functionalized thiacalix[4]arenes (L) and halogen anions X⁻ (X=Cl and Br) under solvothermal conditions. Remarkably, catalysts 1-Cl and 1-Br exhibit great stability in aqueous solutions over a wide pH range. Significantly, MOFs 1-Cl and 1-Br , as recycled heterogeneous catalysts, are capable of highly efficient catalysis for click reactions in water. The MOF structures, especially the exposed active Cu^I sites and 1D channels, play a key role in the improved catalytic activities. In particular, their catalytic activities in water are greatly superior to those in organic solvents or even in mixed solvents. This work proposes an attractive route for the design and self-assembly of environmentally friendly MOFs with high catalytic activity and reusability in water.     

Four novel linear trinuclear assemblies containing bridging triazole ligands. Crystal structure,magnetic, semiconducting and fluorescent properties

Four homotrinuclear linear coordination compounds with bridging ligand of (m-phenol)-1,2,4-triazole, [Mn₃(L)₆(H₂O)₆](ClO₄)₆ (1), [Ni₃(L)₆(H₂O)₆](BF₄)₆·4DMF (2), [Cd₃(L)₆(H₂O)₆](ClO₄)₆· 2H₂O·2DMF·2EtOH (3), [Zn₃(L)₈(H₂O)₄](BF₄)₄(SiF₆)·2EtOH·12H₂O (4), have been synthesized and structurally determined. The structures consist of three metal ions in linear arrangements, linked to each other by two pairs of three N1, N2 bridging triazole ligands. The negative value of J suggests that antiferromagnetic interaction exists in 1. Green fluorescence of 2 and 4 with emissions at 518 nm for 2 and 524 for 4 is possibly assigned to LMCT. The energy gaps of the compounds 2 and 4 are 1.82 and 1.97 eV, respectively, which suggests that the two materials behave as semiconductors.     

Structural Transformations and Spin-Crossover in [FeL2]2+ Salts (L=4-{tert-Butylsulfanyl}-2,6-di{pyrazol-1-yl}pyridine): The Influence of Bulky Ligand Substituents

4-(tert-Butylsulfanyl)-2,6-di(pyrazol-1-yl)pyridine (L) was obtained in low yield from a one-pot reaction of 2,4,6-trifluoropyridine with 2-methylpropane-2-thiolate and sodium pyrazolate in a 1:1:2 ratio. The materials [FeL₂][BF₄]₂⋅solv ( 1[BF₄]₂ ⋅solv) and [FeL₂][ClO₄]₂⋅solv ( 1[ClO₄]₂ ⋅solv; solv=MeNO₂, MeCN or Me₂CO) exhibit a variety of structures and spin-state behaviors including thermal spin-crossover (SCO). Solvent loss on heating 1[BF₄]₂ ⋅x MeNO₂ (x≈2.3) occurs in two steps. The intermediate phase exhibits hysteretic SCO around 250 K, involving a “reverse-SCO” step in its warming cycle at a scan rate of 5 K min⁻¹. The reverse-SCO is not observed in a slower 1 K min⁻¹ measurement, however, confirming its kinetic nature. The final product [FeL₂][BF₄]₂⋅0.75 MeNO₂ was crystallographically characterized, and shows abrupt but incomplete SCO at 172 K which correlates with disorder of an L ligand. The asymmetric unit of 1[BF₄]₂ ⋅y Me₂CO (y≈1.6) contains five unique complex molecules, four of which undergo gradual SCO in at least two discrete steps. Low-spin 1[ClO₄]₂ ⋅0.5 Me₂CO is not isostructural with its BF₄⁻ congener, and undergoes single-crystal-to-single-crystal solvent loss with a tripling of the crystallographic unit cell volume, while retaining the P space group. Three other solvate salts undergo gradual thermal SCO. Two of these are isomorphous at room temperature, but transform to different low-temperature phases when the materials are fully low-spin.