Triangular Dodecahedron Research Articles

Keeping dysprosium in line: Trinuclear heterometallic MII2DyIII complexes with M=Cd, Co and Cu

AbstractFour new heterometallic trinuclear essentially linear (“in‐line”) MII2DyIII complexes (M=CdII (1), CoII (2), CuII (3, 4) were synthesised using the ligand 3,5‐di‐tert‐butylbenzoic acid (dtbbaH) in a MeCN : iPrOH (1–3) or in a MeOH : iPrOH : DMF (4) mixture. Single crystal structure analyses revealed the formation of [Cd2Dy(dtbba)6(iPrOH)2(H2O)2NO3] ⋅ iPrOH (1), [Co2Dy(dtbba)6(iPrOH)2(H2O)2NO3] ⋅ iPrOH (2), [Cu2Dy(dtbba)6(MeCN)4NO3] ⋅ MeCN (3) and [Cu2Dy(dtbba)6(iPrOH)1.68(DMF)1.32(H2O)NO3] ⋅ 3iPrOH ⋅ H2O (4). The M−Dy−M angles become more acute from (1) to (3) leading to decreased M⋅⋅M distances. The DyIII ions are 8‐coordinate with a distorted triangular dodecahedron geometry and a D2d symmetry whereas the geometry of the 5‐coordinate terminal MII ions can best be described as either distorted vacant octahedra or as spherical square pyramids with a C4v symmetry. Magnetic susceptibility measurements were performed on (1), (2) and (3) which allows a comparison of the effect of replacing highly anisotropic CoII with the quantum spin of CuII. Both (2) and (3) show effects of ferromagnetic interactions at low temperatures.

Front Cover: Syntheses, Polymorphic Transformations, and Functions of Ionic Crystals Based on Mononuclear Bismuth(III) Complexes and Polyoxometalates (ChemNanoMat 5/2022)

Polyoxometalates (POMs) have been a popular motif in crystal engineering. In this work, seven ionic crystals based on Keggin- or Dawson-type POMs and mononuclear Bi(III) complexes were synthesized. The Bi(III) center exhibited triangular dodecahedron, square antiprism, or pseudo-cubic eight-coordination geometries, with DMSO or DMF as ligands. The ionic crystals showed polymorphic transformations, and high proton conductivities depending on the structure. More information can be found in the Research Article by Sayaka Uchida et al.

Salts of Lanthanide(III) Hexafluoroacetylacetonates [Ln = Sm(III), Eu(III) and Tb(III)] with Dipyridylammonium cations: Synthesis, characterization, photophysical properties and OLED fabrication

A series of tetrakis lanthanide complexes with the general formula [Ln(hfaa)4]-(DpaH)+ [Ln = (Sm-1), (Eu-1) and (Tb-1)], hfaa = hexafluroacetylacetonate and Dpa −2,2′-dipyridylamine] has been synthesized by the reaction of LnCl3, hfaa and Dpa in the presence of ammonia solution (25%). The complexes have been characterized by analytical and spectroscopic methods. The solution molecular structure of the complexes was elucidated by one- and two-dimensional NMR spectroscopy which shows that the DpaH+ cation retains a close interaction with the lanthanide anion in solution. The crystal structure of Eu-1, determined by single crystal X-ray diffraction, confirms this intermolecular interaction in the solid-state through a N–H⋯O hydrogen bond of 2.187 Å. In the [Eu(hfaa)4]- anion the EuO8 coordination polyhedron has a distorted triangular dodecahedron geometry with approximate D2d-symmetry around the metal centre. Photophysical, thermal, and electroluminescent properties of the complexes have been investigated. The Sm-1 and Eu-1 complexes displayed efficient typical red emission with a sizeable photoluminescence quantum yield (PLQY) while Tb-1 displayed near-white light emission. The complexes have been used as dopants to fabricate single- and double-emitting layer (EML) OLEDs through the thermal evaporation method. At the optimum doping concentration, double-EML Eu-1 based device displayed orange electroluminescence (EL) with a brightness (B) of 417 cd/m2 and very low Vturn-on = 3.4 V. Interestingly, the Sm-1 based single-EML device exhibited pure red emission with the Commission internationale de l'éclairage [(CIE)x,y = 0.613, 0.321], which is rare. The Sm-1 based device performance [B = 145 cd/m2, current efficiency (ηc) = 0.35 cd/A, power efficiency (ηp) = 0.15 lm/W with an external quantum efficiency (EQE) = 0.3% and Vturn-on = 7.1 V] surpassed that of the only reported Sm-based single red-OLED (R-OLED).

Syntheses, Polymorphic Transformations, and Functions of Ionic Crystals Based on Mononuclear Bismuth(III) Complexes and Polyoxometalates

AbstractThe controlled assembly of molecules, ions, and ligands as building blocks based on crystal engineering leads to various functional crystalline solids. In particular, polyoxometalates (POMs), which are anionic metal oxide clusters, have been a popular motif in crystal engineering. To revisit simple mononuclear metal complexes as counter cations of POMs, seven ionic crystals based on Keggin‐ or Dawson‐type POMs with mononuclear bismuth(III) complexes as counter cations were synthesized. The bismuth(III) center exhibited triangular dodecahedron, square antiprism, or pseudo‐cubic eight‐coordination geometries, with dimethyl sulfoxide or N,N‐dimethylformamide as ligands. The ionic crystals showed polymorphic transformation depending on the synthetic or recrystallization conditions. As a method for exploring functionality, proton conductivities of the ionic crystals were measured under humidified conditions. The ionic crystals with high porosity, tertiary amine moieties, or coordination water exhibited high proton conductivities, and large activation energies indicate that protons are transferred mainly with water molecules via the vehicle mechanism.

Zero‐field Slow Magnetic Relaxation Behavior of Dy2 in a Series of Dinuclear {Ln2} (Ln=Dy, Tb, Gd and Er) Complexes: A Combined Experimental and Theoretical Study

AbstractA series of dinuclear lanthanide(III) complexes having general formulae [Ln2L2(thd)4] ⋅ 2CH3CN {Ln=DyIII(1), TbIII(2), GdIII(3), ErIII(4)} were successfully synthesized using Schiff base (E)‐2‐((pyridin‐2‐ylmethylene)amino)phenol (LH) and co‐ligand 2,2,6,6‐Tetramethyl‐3,5‐heptanedione (Hthd). The single crystal XRD data shows that complexes possess a dinuclear planar [Ln2(μ2‐O)2]4+ core where phenolate oxygen atoms act as bridges between the two LnIII ions, and that the coordination sphere of LnIII with eight coordination has distorted trigonal dodecahedron geometry. The magnetic analysis shows complex 1 is a single molecule magnet having a zero‐field effective energy barrier (Ueff) of 54.02 K and relaxation time of τo=4.45×10−6 s. Field‐induced SMM behavior has been observed for 4 with an effective energy barrier of 26.9 K and τ0=2.4×10−9 s. CASSCF+RASSI‐SO calculations on 1, 2 and 4 provide deep insight regarding the electronic structure and single‐ion anisotropy of lanthanide ions. Further, using state‐of‐the‐art ab initio calculations, the nature of magnetic anisotropy and magnetic exchange interaction between the LnIII centers is analyzed to shed light on the magnetic dynamics of all the complexes 1–4.

Pseudo-mono-axial ligand fields that support high energy barriers in triangular dodecahedral Dy(iii) single-ion magnets.

The synthesis of air-stable, high-performance single-molecule magnets (SMMs) is of great significance for their practical applications. Indeed, Ln complexes with high coordination numbers are satisfactorily air stable. However, such geometries easily produce spherical ligand fields that minimize magnetic anisotropy. Herein, we report the preparation of three air-stable eight-coordinate mononuclear Dy(iii) complexes with triangular dodecahedral geometries, namely, [Dy(BPA-TPA)Cl](BPh4)2 (1) and [Dy(BPA-TPA)(X)](BPh4)2·nCH2Cl2 (X = CH3O- and n = 1 for 2; L = PhO- and n = 2 for 3), using a novel design concept in which the bulky heptadentate [2,6-bis[bis(2-pyridylmethyl)amino]methyl]-pyridine (BPA-TPA) ligand enwraps the Dy(iii) ion through weak coordinate bonds leaving only a small vacancy for a negatively charged (Cl-), methoxy (CH3O-) or phenoxy (PhO-) moiety to occupy. Magnetic measurements reveal that the single-molecule magnet (SMM) property of complex 1 is actually poor, as there is almost no energy barrier. However, complexes 2 and 3 exhibit fascinating SMM behavior with high energy barriers (U eff = 686 K for 2; 469 K for 3) and magnetic hysteresis temperatures up to 8 K, which is attributed to the pseudolinear ligand field generated by one strong, highly electrostatic Dy-O bond. Ab initio calculations were used to show the apparent difference in the magnetic dynamics of the three complexes, confirming that the pseudo-mono-axial ligand field has an important effect on high-performance SMMs compared with the local symmetry. This study not only presents the highest energy barrier for a triangular dodecahedral SMM but also highlights the enormous potential of the pseudolinear Dy-L ligand field for constructing promising SMMs.

Crystal structure and Hirshfeld surface analysis of the anionic tetra-kis-complex of lanthanum(III) NMe4LaL 4 with the CAPh-ligand dimeth-yl (2,2,2-tri-chloro-acet-yl)phospho-ramidate.

The anionic tetra-kis-complex of lanthanum(III) NMe4LaL 4 with the CAPh-ligand dimethyl (2,2,2-tri-chloro-acet-yl)phospho-ramidate (HL), namely, tetra-methyl-ammonium tetra-kis-{2,2,2-tri-chloro-1-[(di-meth-oxy-phosphor-yl)imino]-ethano-lato}lanthanum(III), (C4H12N)[La(C4H6Cl3NO4P)4], has been synthesized, crystallized and structurally characterized by X-ray diffraction. The lanthanide ion is surrounded by four anionic, bis-chelating CAPh ligands forming the complex anion with a coordination number of eight for La3+ and NMe4 + as the counter-ion. The coordination polyhedron of the La3+ ion was inter-preted as a triangular dodeca-hedron.

Structure elucidation by Sparkle/RM1, and solution behavior of lanthanideIII complexes: NMR, 4f‒4f absorption spectra and Photoluminescent properties

This paper presents the paramagnetic NMR, 4f‒4f absorption and photoluminescence properties of the complexes of Sm, Eu, Ho and Er with hexafluoroacetylacetone (hfaa) and 1,10‒phenanthroline (phen) in various coordinating and non‒coordinating solvents. The ground state molecular structure of the ternary complexes, [Ln(hfaa)3(phen)](Ln = Ho and Er) and their hydrated parent molecules, [Ln(hfaa)3(H2O)2] were determined using semi‒empirical Sparkle/RM1 method. The optimized structures reflect the effect of lanthanide contraction as the average bond distances [Ln‒O and Ln‒N] decreases on going from Ho to Er. The shape analyses reveal that the geometry of these eight-coordinated complexes is very close to triangular dodecahedron with D2d symmetry. The NMR spectra of the complexes show that the complexes are stable in both coordinating and non‒coordinating solvents. In the 4f‒4f absorption spectra, the solvents’ effect is reflected on the band shape and oscillator strength of the hypersensitive transitions of ternary Ho (5G6 ← 5I8) and Er (2H11/2 ← 4I15/2 and 4G11/2 ← 4I15/2) complexes. These changes suggest solvents influence in changing the symmetry of the field around the Ho and Er ions. The photophysical properties of Sm and Eu complexes are superior in non‒coordinating solvents than those observed in the coordinating solvents .

Li3La[PS4]2: The First Lithium Lanthanum Ortho‐Thiophosphate

AbstractThe first lithium‐containing lanthanum ortho‐thiophosphate(V) with the formula Li3La[PS4]2 crystallizes orthorhombically in the space group Pbca with a=1053.51(6) pm, b=1920.62(11) pm, c=1165.83(7) pm and Z=8. Colorless single crystals were obtained from the reaction of lanthanum trichloride, dilithium sulfide and diphosphorus pentasulfide at 750 °C with lithium chloride as by‐product. The new structure of Li3La[PS4]2 features characteristic [PS4]3− anions and a crystallographically unique La3+‐cation position, surrounded by eight sulfur atoms from four [PS4]3− tetrahedra constructing a trigonal dodecahedron. These [LaS8]13− polyhedra are connected via [PS4]3− tetrahedra to form strongly corrugated layers ( ) spreading out parallel to the ac‐plane with Li+ cations in between residing in four‐, five‐ and sixfold sulfur coordination. Raman‐spectroscopic measurements were performed to visualize further vibrational modes, whereas diffuse reflectance spectroscopy verified the absorption of UV light, owing to the colorless appearance of the crystals. The optical band gap was found to be at 3.25 eV. Energy‐dispersive X‐ray spectroscopy (EDXS) measurements assured the absence of chlorine in the investigated single crystals. Calculations of Effective Coordination Numbers (ECoN) for each crystallographic position confirm the refined coordination environments for all atoms. Further investigations of the Madelung Parts of the Lattice Energies (MAPLE) point out the strong relationship of Li3La[PS4]2 with the ternary compounds of Li3[PS4] and La[PS4].

Calcium Chelidonate: Semi-Synthesis, Crystallography, and Osteoinductive Activity In Vitro and In Vivo.

Calcium chelidonate [Ca(ChA)(H2O)3]n was obtained by semi-synthesis using natural chelidonic acid. The structure of the molecular complex was determined by X-ray diffraction analysis. The asymmetric unit of [Ca(ChA)(H2O)3]n includes chelidonic acid coordinated through three oxygen atoms, and three water ligands. The oxygen atoms of acid and oxygen atoms of water from each asymmetric unit are also coordinated to the calcium of another one, forming an infinite linear complex. Calcium geometry is close to the trigonal dodecahedron (D2d). The intra-complex hydrogen bonds additionally stabilize the linear species, which are parallel to the axis. In turn the linear species are packed into the 3D structure through mutual intercomplex hydrogen bonds. The osteogenic activity of the semi-synthetic CaChA was studied in vitro on 21-day hAMMSC culture and in vivo in mice using ectopic (subcutaneous) implantation of CaP-coated Ti plates saturated in vitro with syngeneic bone marrow. The enhanced extracellular matrix ECM mineralization in vitro and ectopic bone tissue formation in situ occurred while a water solution of calcium chelidonate at a dose of 10 mg/kg was used. The test substance promotes human adipose-derived multipotent mesenchymal stromal/stem cells (hAMMSCs), as well as mouse MSCs to differentiate into osteoblasts in vitro and in vivo, respectively. Calcium chelidonate is non-toxic and can stimulate osteoinductive processes.

Influence of the Different Types of Auxiliary Noncarboxylate Organic Ligands on the Topologies and Magnetic Relaxation Behavior of Zn-Dy Heterometallic Single Molecule Magnets.

In this work, we first synthesized a Zn-Dy complex, [Zn6Dy2(L)6(tea)2(CH3OH)2]·6CH3OH·8H2O (H2L = N-3-methoxysalicylidene-2-amino-3-hydroxypyridine, teaH3 = triethanolamine, 1), by employing H2L, anhydrous ZnCl2, and Dy(NO3)3·5H2O reacting with auxiliary ligand teaH3 in the mixture of CH3OH and DMF. When teaH3 and the solvent CH3OH in the reaction system of 1 were replaced by the auxiliary ligand 2,6-pyridinedimethanol (pdmH2) and the solvent MeCN, another Zn-Dy complex, [Zn4Dy4(L)6(pdm)2(pdmH)4]·10CH3CN·5H2O (2), was obtained. For 1, its crystal structure can be viewed as a dimer of two Zn3DyIII units. However, for 2, four DyIII form a zigzag arrangement, and each of its terminals linked two ZnII ions. Interestingly, although the structural topologies of 1 and 2 are different, the coordination geometries of DyIII in 1 and 2 are all triangular dodecahedron (TDD-8). The difference is that the continuous shape measure (CShM) values of DyIII in 1 are larger than the corresponding values in 2. Magnetic investigation revealed that the diluted sample 1@Y exhibits two magnetic relaxation processes, while 2 only exhibits a single relaxation process. Ab initio calculations indicated that, in the crystal lattice of 1, two complexes exhibiting slightly different CShM values of DyIII result in the double relaxation behavior of 1@Y. However, for 2, one of two DyIII fragments possesses a fast quantum tunneling of magnetization (QTM), resulting in its magnetic process presented at T < 1.8 K, so 2 exhibits single relaxation behavior. More importantly, the theoretical calculations also clearly indicated that the weak ligation at equatorial sites of DyIII in 1 and 2 ensure 1@Y and 2 possess SMM behavior, although the coordination geometry of DyIII (TDD-8) in 1 and 2 severely deviates from the ideal polyhedron and its axial symmetry is low.

Novel isopolymolybdates with different configurations of hexagram, double dish, and triangular dodecahedron

Novel isopolymolybdates [MoO3]n (1), Na8(Et4N)2[Mo12O30(SO3)2(HSO3)6]·8H2O (2), Na6(Et4N)5[Mo12O30(SO4)2(SO3)(HSO3)5]·14H2O (3) and [Mo16O52]·10NH(CH3)2 (4) were obtained and well-characterized with different configurations of hexagram, double dish and triangular dodecahedron. The hexagram-type units Mo12O36 in 1 are connected in a 3D structure with 5.7 ​Å diameter tunnels, which can adsorb a small amount of O2 (11.00 ​mg/g) at 29.9 ​bar, while no adsorption was found for H2/CH4/CO2/N2. The two coplanar {Mo6} rings in polyoxomolybdenum sulfites 2 and 3 are linked by central sodium atom to form a “double dish type” fashion. The triangular dodecahedron type of isopolymolybdate 4 consists of mixed valence [MoV3O7]4 and [MoVIO6]4 units, which are spatially arranged in the position of the vertices of the tetrahedron.

Regulating the magnetic dynamics of mononuclear β-diketone Dy(iii) single-molecule magnets through the substitution effect on capping N-donor coligands.

A series of five mononuclear β-diketonate-Dy(iii) complexes, with formulas Dy(ntfa)3(Br-bpy) (1), Dy(ntfa)3(Br2-bpy) (2), Dy(ntfa)3(5,5-(CH3)2-bpy) (3), Dy(ntfa)3(4,4-((CH3)3)2-bpy) (4) and Dy(ntfa)3(4,4-(CH3)2-bpy) (5) (ntfa = 4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedione, Br-bpy = 5-bromo-2,2'-bipyridine, Br2-bpy = 4,4'-dibromo-2,2'-bipyridine, 5,5-(CH3)2-bpy = 5,5'-di-methyl-2,2'-bipyridine, 4,4-((CH3)3)2-bpy = 4,4'-di-tert-butyl-2,2'-bipyridine, and 4,4-(CH3)2-bpy = 4,4'-di-methyl-2,2'-bipyridine), have been prepared by altering the capping N-donor coligands. Dy(iii) ions in all complexes possess N2O6 octa-coordinated environments, displaying a distorted square antiprismatic D4d symmetry in complexes 1-4, as well as a triangular dodecahedron D2d symmetry in 5. Magnetic investigations evidence the SIM behavior in the five complexes with the energy barriers (Ueff) of 104.19 K (1), 122.93 K (2), 84.20 K (3), 64.16 K (4) and 80.23 K (5) under zero applied dc field. The potential QTM effects in the title complexes are successfully suppressed in the presence of the extra applied fields. The crystal field parameters and orientations of the magnetic easy axes were obtained from the simulation of the magnetic data and the electrostatic model calculation. The distinct electronic effects originating from the subtle changes of the substituents on the capping N-donor coligands induce varying coordination microenvironments and geometries on the Dy(iii) sites, further drastically impacting the overall magnetic properties of the title complexes. The disparities of the uniaxial anisotropy and the magnetic dynamics for 1-5 have been elucidated by ab initio calculations as well.

Magnetic Molecular Rectangles Constructed from Functionalized Nitronyl‐Nitroxide Ligands and Lanthanide(III) Ions

AbstractFive binuclear complexes with rectangular topology have been synthesized using a nitronyl‐nitroxide ligand (L) functionalized with a pyrazole coordinating group: [Ln2(hfac)2L2], with Ln=Eu (1), Gd (2 a, 2 b), Tb (3), Dy (4), Tm (5). The EuIII and TmIII complexes crystallize in the P21/n space group, while the GdIII, TbIII, and DyIII derivatives crystalize in P‐1 space group. The crystal structures for compounds 2 a, 3, 4, and 5 have been fully solved, while for compounds 1 and 2 b, the unit cell parameters have been measured and compared with crystals 3 and 5. Crystals 2 a (P21/n) and 2 b (P‐1) are polymorphic forms. In these complexes the nitronyl‐nitroxide ligand bridges two metal ions through one aminoxyl group and the pyrazole fragment. In the five complexes the LnIII ions show a coordination number of eight with a triangular dodecahedron geometry. The magnetic properties of all five complexes have been investigated. For compounds 2, 3, and 4 the LnIII‐Rad interaction was found to be ferromagnetic: JGdRad=2.09(1) cm−1 [H=‐2JGdRad(SGd1SRad1+SGd2SRad2], JTbRad=1.93(14) cm−1, JDyRad=1.72(14) cm−1. The TmIII‐Rad coupling is antiferromagnetic (JTmRad=−0.53(1) cm−1). For the TbIII, DyIII, and TmIII complexes the effects of the crystal field have been taken into account in the fitting procedure.

A series of mononuclear Ln-radical complexes based on 1-methylpyrazole nitronyl nitroxide: Synthesis, structure and magnetic properties

The reaction of LnIII salts (GdIII, TbIII and DyIII) and the 1-methyl-3-pyrazole nitronyl nitroxide radical gives three isostructural complexes, namely [Ln(hfac)3(1-Me-3-NIT-Pyz)] (Ln = Gd (1), Tb (2) and Dy (3); 1-Me-3-NIT-Pyz = 2-[3-(1-methyl-pyrazolyl)]-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide; hfac = hexafluoroacetylacetone). Single crystal X-ray diffraction studies showed that all three complexes are composed of two independent mononuclear bi-spin systems, in which the central LnIII ions are eight-coordinated with three bidentate hfac− ions and one bidentate chelating 1-Me-3-NIT-Pyz radical. The coordination polyhedron of the central LnIII ions can be described as a triangular dodecahedron (D2d). In addition, there exist weak ferromagnetic couplings in the GdIII-NIT radical system in complex 1 based on magnetic fitting. Dynamic magnetic studies show that the out-of-phase component of the ac-magnetic susceptibilities of complexes 2 and 3 exhibit a certain degree of frequency dependence and the two complexes do not show any obvious magnetic relaxation behavior.

A new mononuclear terbium and copper cocrystalline nitronyl nitroxide complex: synthesis, structure and magnetic properties

One 2p-3d-4f multispin complex [Cu(hfac)(4-Me-3-NITtrz)2][Tb(hfac)4]·H2O (1) has been obtained based on a functionalized nitronyl nitroxide radical 4-Me-3-Nit-trz (in which, 4-Me-3-Nit-trz = 2-[3-(4-methyl-l,2,4-triazolyl)]-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, hfac = hexafluoroacetylacetone). Complex 1 crystallizes in tetragonal system, I4¯ space group. The central CuII ion is six-coordinated in tensile octahedron configuration finished by two bidentate radical ligands and one bidentate hfac anion, while TbIII ion exhibited as distorted triangular dodecahedron geometry (D2d) finished by eight oxygen atoms from four bischelate hfac anions. Magnetic studies show that Cu(II) ion and the NO group are antiferromagnetically coupled with coupling constants of JCu–rad = 1.76~1.99 cm−1, and strong antiferromagnetic exchange interactions between the two intramolecular radicals with Jrad–rad = -12.88~-10.42 cm−1 exist in 1. In addition, alternating current (ac) magnetic susceptibilities were further measured.

Synthesis, Structures, and Magnetic Properties of Zigzag Tetranuclear Lanthanide Complexes

Five isostructural tetranuclear lanthanide complexes with the general formula [Ln4(teaH2)2(teaH)2(NO3)6]·2CH3OH [Ln3+ = Dy3+ (1), Tb3+ (2), Ho3+ (3), Er3+ (4), and Gd3+ (5)] were successfully synthesized by the reaction of various lanthanide nitrate and triethanolamine (teaH3) ligand. Single crystal X‐ray analyses reveal the eight‐coordinate Ln3+ centers adopt a slightly distorted triangular dodecahedron geometry and nine‐coordinate Ln3+ ions own an approximately capped square antiprism environment in similar zigzag Ln4 core. Magnetic studies demonstrate the presence of anitferromagnetic interactions between Ln3+ centers without obvious SMM behavior.

Octacoordinated tin(IV) complexes bearing oxy-p-benzoquinone and oxy-p-iminobenzoquinone ligands: Structural investigations and dynamics of coordination sphere in solution

Two new hypercoordinated tin(IV) complexes bearing 2-hydroxy-3,6-di-tert-butyl-p-benzoquinone (L1H) and 2-hydroxy-3,6-di-tert-butyl-N-phenyl-p-iminobenzoquinone (L2H) ligands were synthesized and investigated using IR-, UV–Vis, NMR spectroscopy and X-ray diffraction. The rare examples of octacoordinated tin compounds are realized by four bidentate ligands L1 (in 1) or L2 (in 2) bonded with metal center. Complexes are characterized by irregular bicapped trigonal prismatic distorted toward the idealized dodecahedron geometry of coordination polyhedron in crystals according to the X-ray diffraction. The dynamic transformation between bicapped trigonal prismatic and dodecahedron configurations of coordination polyhedra was found and investigated in solution of 1 and 2 by means of Variable Temperature NMR spectroscopy.

A series of mononuclear lanthanide complexes constructed by Schiff base and β-diketonate ligands: synthesis, structures, magnetic and fluorescent properties

The Schiff base H2bcsdt (H2bcsdt = N1,N3-bis(5-chlorosalicyladehyde) diethylenetriamine) and the β-diketonate Hdbm (Hdbm = dibenzoylmethane) have been employed as a ligand and a pro-ligand to construct a series of Ln(III) complexes. Five mononuclear compounds were synthesized under solvothermal conditions. Single-crystal X-ray diffraction analyses reveal that they are formulated as [Ln(bcsdt)(dbm)(H2O)]·MeCN (Ln = Gd (1), Tb (2), Dy (3), Ho (4), Er (5)). The metal ions in complexes 1–5 are all eight-coordinated and display a similar capped triangular dodecahedron (D2h) geometry. The fluorescent and magnetic properties of 1–5 were investigated. Complex 2 exhibits an intense green luminescence emission which is characteristic of the Tb(III) ion. Weak intermolecular antiferromagnetic interactions were determined in 2–5.

Coordination Polymer and Monomer with the Cd(NO3)2 Fragment Containing 2-Amino-5-Bromopyridine: Synthesis, Structures, NMR Study, and Luminescence Properties

The reactions of Cd(NO3)2 ⋅ 4H2O with 2-amino-5-bromopyridine (Аbp) afford compounds [Cd(NO3)2(Аbp)(H2O)]n (I) and [Cd(NO3)2(Abp)2(H2O)2] (II). The structures of both complexes are determined by single-crystal X-ray structure analysis (CIF files CCDC nos. 1938624 (I) and 1959680 (II)). Compound I is a coordination 1D polymer in which two chelate-bonded $${\text{NO}}_{3}^{ - }$$ groups act as bridges. The coordination polyhedron of the octacoordinated central cadmium atom in compound I consists of seven oxygen atoms (one oxygen atom of water and six atoms of the $${\text{NO}}_{3}^{ - }$$ groups) and one nitrogen atom of Abp, being a triangular dodecahedron. Complex II is a mononuclear molecule in which the octahedral coordination polyhedron of Cd is formed by four oxygen atoms of two water molecules and two $${\text{NO}}_{3}^{ - }$$ groups and two oxygen atoms of two molecules of the Abp cycle. In both complexes, the amino group of Abp is not involved in coordination with the metal. Compound I is studied by 1H, 31C, and 15N NMR spectroscopy of a solution of the polymer complex in CD3CN, and the most substantial difference in the chemical shifts of the bound and free Abp ligands is observed in the 15N NMR spectra (37 ppm). According to the data of luminescence spectroscopy, compounds I and II exhibit an emission in a range of 430–690 nm.