RESUMEN
A new binary organic salt diphenyl diisopropylamino phosphonium hexaflurophosphate (DPDPâ PF6 ) was shown to exhibit a good ferroelectric response and employed for mechanical energy harvesting application. The phosphonium salt crystallizes in the monoclinic noncentrosymmetric space group Cc and exhibits an H-bonded 1D chain structure due to N-Hâ â â F interactions. Ferroelectric measurements on the single crystals of DPDPâ PF6 gave a well-saturated rectangular hysteresis loop with a remnant (Pr ) polarization value of 6â µC cm-2 . Further, composite devices based on polydimethylsiloxane (PDMS) films for various weight percentages (3, 5, 7, 10 and 20â wt %) of DPDPâ PF6 were prepared and examined for power generation by using an impact test setup. A maximum output peak-to-peak voltage (VPP ) of 8.5â V and an output peak-to-peak current (IPP ) of 0.5â µA was obtained for the non-poled composite film with 10â wt % of DPDPâ PF6 . These results show the efficacy of organic ferroelectric substances as potential micropower generators.
RESUMEN
A charge-neutral tetrahedral [(Pd3X)4L6] cage assembly built from a trinuclear polyhedral building unit (PBU), [Pd3X](3+), cis-blocked with an imido P(V) ligand, [(N(i)Pr)3PO](3-) (X(3-)), and oxalate dianions (L(2-)) is reported. Use of benzoate or ferrocene dicarboxylate anions, which do not offer wide-angle chelation as that of oxalate dianions, leads to smaller prismatic clusters instead of polyhedral cage assemblies. The porosity of the tetrahedral cage assembly was determined by gas adsorption studies, which show a higher uptake capacity for CO2 over N2 and H2. The tetrahedral cage was shown to encapsulate a wide range of neutral guest solvents from polar to nonpolar such as dimethyl sulfoxide, benzene, dichloromethane, chloroform, carbon tetrachloride, and cyclopentane as observed by mass spectral and single-crystal X-ray diffraction studies. The (1)H two-dimensional diffusion ordered spectroscopy NMR analysis shows that the host and guest molecules exhibit similar diffusion coefficients in all the studied host-guest systems. Further, the tetrahedral cage shows selective binding of benzene, CCl4, and cyclopentane among other solvents from their categories as evidenced from mass spectral analysis. A preliminary density functional theory analysis gave a highest binding energy for benzene among the other solvents that were structurally shown to be encapsulated at the intrinsic cavity of the tetrahedral cage.
Asunto(s)
Modelos Moleculares , Paladio/química , Cristalografía por Rayos X , Espectroscopía de Resonancia Magnética , Simulación de Dinámica MolecularRESUMEN
The homometallic hexameric ruthenium cluster of the formula [Ru(III)6(µ3-O)2(µ-OH)2((CH3)3CCO2)12(py)2] (1) (py = pyridine) is solved by single-crystal X-ray diffraction. Magnetic susceptibility measurements performed on 1 suggest that the antiferromagnetic interaction between the Ru(III) centers is dominant, and this is supported by theoretical studies. Theoretical calculations based on density functional methods yield eight different exchange interaction values for 1: J1 = -737.6, J2 = +63.4, J3 = -187.6, J4 = +124.4, J5 = -376.4, J6 = -601.2, J7 = -657.0, and J8 = -800.6â cm(-1). Among all the computed J values, six are found to be antiferromagnetic. Four exchange values (J1, J6, J7 and J8) are computed to be extremely strong, with J8, mediated through one µ-hydroxo and a carboxylate bridge, being by far the largest exchange obtained for any transition-metal cluster. The origin of these strong interactions is the orientation of the magnetic orbitals in the Ru(III) centers, and the computed J values are rationalized by using molecular orbital and natural bond order analysis. Detailed NMR studies ((1)H, (13)C, HSQC, NOESY, and TOCSY) of 1 (in CDCl3) confirm the existence of the solid-state structure in solution. The observation of sharp NMR peaks and spin-lattice time relaxation (T1 relaxation) experiments support the existence of strong intramolecular antiferromagnetic exchange interactions between the metal centers. A broad absorption peak around 600-1000â nm in the visible to near-IR region is a characteristic signature of an intracluster charge-transfer transition. Cyclic voltammetry experiments show that there are three reversible one-electron redox couples at -0.865, +0.186, and +1.159â V with respect to the Ag/AgCl reference electrode, which corresponds to two metal-based one-electron oxidations and one reduction process.
Asunto(s)
Oxígeno/química , Piridinas/química , Rutenio/química , Cristalografía por Rayos X , Dimerización , Espectroscopía de Resonancia Magnética , Imanes/química , Modelos Moleculares , Piridinas/síntesis química , Teoría Cuántica , Espectroscopía Infrarroja por Transformada de FourierRESUMEN
Herein we report the synthesis and structures of [(CH3)2NH2]Er(HCO2)2(C2O4) and [(NH2)3C]Er(HCO2)2(C2O4), in which the inclusion of divalent oxalate ligands allows for the exclusive incorporation of A+ and B3+ cations in an ABX3 hybrid perovskite structure for the first time. We rationalise the observed thermal expansion of these materials, including negative thermal expansion, and find evidence for weak antiferromagnetic coupling in [(CH3)2NH2]Er(HCO2)2(C2O4).
RESUMEN
By employing a tridentate thiophosphoramide ligand, [(NHAQ)3P[double bond, length as m-dash]S] (AQ = 3-quinolinyl), a cationic MOF, {[Cu6I5(L(1))2](OH)·3DMF·2.5MeOH}n, was synthesized. Photo-physical studies on the 2D-MOF showed an unusual thermochromic behaviour emitting a blue fluorescence at 298 K due to the AQ chromophore and an orange-yellow phosphorescence at 77 K due to the [Cu6I5](+) unit.
Asunto(s)
Cobre/química , Yoduros/química , Compuestos Organometálicos/química , Compuestos Organometálicos/síntesis química , Fosforamidas/química , Termodinámica , Cationes , Ligandos , Modelos Moleculares , Estructura Molecular , FotoquímicaRESUMEN
We establish the coordination potential of the Schiff base ligand (2-methoxy-6-[(E)-2'-hydroxymethyl-phenyliminomethyl]-phenolate (H2L)) via the isolation of various M(II)-Ln(III) complexes (where M(II) = Ni or Zn and Ln(III) = La or Pr or Gd). Single crystals of these five complexes were isolated and their solid state structures were determined by single crystal X-ray diffraction. Structural determination revealed molecular formulae of [NiGd(HL)2(NO3)3] (1), [NiPr(HL)2(NO3)3] (2) and [Ni2La(HL)4(NO3)](NO3)2 (3), [Zn2Gd(HL)4(NO3)](NO3)2 (4), and [Zn2Pr(HL)4(NO3)](NO3)2 (5). Complexes and were found to be neutral heterometallic dinuclear compounds, whereas 3-5 were found to be linear heterometallic trinuclear cationic complexes. Direct current (dc) magnetic susceptibility and magnetization measurements conclusively revealed that complexes 1 and 4 possess a spin ground state of S = 9/2 and 7/2 respectively. Empirically calculated ΔχMT derived from the variable temperature susceptibility data for all complexes undoubtedly indicates that the Ni(II) ion is coupled ferromagnetically with the Gd(III) ion, and antiferromagnetically with the Pr(III) ion in 1 and 2 respectively. The extent of the exchange interaction for was estimated by fitting the magnetic susceptibility data using the parameters (g = 2.028, S = 9/2, J = 1.31 cm(-1) and zJ = +0.007), supporting the phenomenon observed in an empirical approach. Similarly using a HDVV Hamiltonian, the magnetic data of 3 and 4 were fitted, yielding parameters g = 2.177, D = 3.133 cm(-1), J = -0.978 cm(-1), (for 3) and g = 1.985, D = 0.508 cm(-1) (for 4). The maximum change in magnetic entropy (-ΔSm) estimated from the isothermal magnetization data for was found to be 5.7 J kg(-1) K(-1) (ΔB = 7 Tesla) at 7.0 K, which is larger than the -ΔSm value extracted from 4 of 3.5 J kg(-1) K(-1) (ΔB = 7 Tesla) at 15.8 K, revealing the importance of the exchange interaction in increasing the overall ground state of a molecule for better MCE efficiency.