Search results for "Ground state"
showing 10 items of 928 documents
Microwave, High-Resolution Infrared, and Quantum Chemical Investigations of CHBrF2: Ground and v4 = 1 States
2011
A combined microwave, infrared, and computational investigation of CHBrF(2) is reported. For the vibrational ground state, measurements in the millimeter- and sub-millimeter-wave regions for CH(79)BrF(2) and CH(81)BrF(2) provided rotational and centrifugal-distortion constants up to the sextic terms as well as the hyperfine parameters (quadrupole-coupling and spin-rotation interaction constants) of the bromine nucleus. The determination of the latter was made possible by recording of spectra at sub-Doppler resolution, achieved by means of the Lamb-dip technique, and supporting the spectra analysis by high-level quantum chemical calculations at the coupled-cluster level. In this context, the…
Spectroscopic and theoretical study of push-pull chromophores containing thiophene-based quinonoid structures as electron spacers
2003
Donor−acceptor chromophores containing three different types of thiophene-based electron spacers and the same donor (1,3-dithiol-2-ylidene) and acceptor (dicyanomethylene) end groups have been investigated by infrared and vis-near-IR absorption spectroscopies with the aim of elucidating the ability of the heteroquinonoid spacers as electron transmitters. Density functional theory calculations have been carried out, both within the standard and the time-dependent formalisms, to assign the most relevant electronic and infrared features of these chromophores and to assess useful information about their molecular structures. Both theoretical calculations and vibrational spectra demonstrate the …
High resolution study of AsHD2: Ground state and the three bending fundamental bands v(3), v(4), and v(6)
2006
International audience; For the first time the infrared spectrum of the AsHD2 molecule has been measured in the region of the bending fundamental bands v(3), v(4), and v(6) on a Fourier transform spectrometer with a resolution of 0.0024 cm(-1) and analyzed. More than 5500 transitions with J(max) = 26 have been assigned and used both to obtain "ground state combination differences" and for the determination of upper state ro-vibrational energies of the triad (001000), (000100), and (000001). Rotational parameters including centrifugal distortion coefficients up to octic terms of the ground vibrational state were calculated by fitting more than 500 "ground state combination differences" with …
Rotational analysis of the v 2 + v 6 ±1, v 5 ∓1 + v 6 ∓1 and v 5 ∓1 + v 6 ±1 interacting infrared bands of methyl bromide
1982
The rotational analysis of the infrared absorption spectrum of CH3 79Br and CH3 81Br between 2150 and 2510 cm-1 was performed on a Fourier transform spectrum with a resolution of 0·007 cm-1. The bands v 2 + v 6(E) and v 5 + v 6(A 1 + A 2 + E) occur in this region, giving rise to several perturbations as in the corresponding system of methyl chloride [3]. Forbidden transitions, observed in correspondence of the level crossing of the x-y Coriolis coupling between v 2 + v 6 and v 5 + v 6(E), enabled us to estimate the value of A″ - 225D″K at 5·16186 cm-1 for CH3 79Br and 5·16173 cm-1 for CH3 81Br. The parallel system of v 5 + v 6 exhibits a perpendicular structure, and an l-type resonance coup…
Synthesis and crystal structure of the low-spin iron(II) complex [Fe(bpym)3](ClO4)2·1/4H2O (bpym=2,2′-bipyrimidine)
1997
Abstract Single crystals of the mononuclear iron(II) complex of formula [Fe(bpym)3](ClO4)2·1/4H2O (bpym=2,2′-bipyrimidine) have been prepared and characterized crystallographically. The complex is monoclinic, P21/c, a=13.688(5), b=19.391(6), c=11.554(5) A, β=102.22(3)°, V=2997(2) A3, Z=4, R=0.063 and Rw=0.068. The structure analysis reveals a distorted octahedral geometry around the iron atom. The average Fe–N bond length and N–Fe–N bidentate angle are 1.970(5) A and 81.0(1)°, respectively. The value of the Fe–N distance and that of the room temperature magnetic moment are in agreement with its singlet 1A1 ground state.
Quaternary Heusler Compounds without Inversion Symmetry: CoFe 1+ x Ti 1– x Al and CoMn 1+ x V 1– x Al
2011
We report the quaternary Heusler compound derivatives CoFe1+xTi1–xAl and CoMn1+xV1–xAl, which do not have centers of inversion. Classical T2T′M (T, T′ = transition metal, M = main group element) Heusler compounds (prototype: Cu2MnAl) crystallize in the L21 structure, space group Fmm (225) that exhibits a center of inversion. Replacing one of the T2 atoms by another transition element (T″) results in a quaternary TT′T″M compound with F3m symmetry (Y; structure type LiMgPdSn) without center of inversion. In the case of “quasi closed shell” compounds with 24 valence electrons in the primitive cell, one expects the absence of ferromagnetism according to the Slater–Pauling rule. Increasing the n…
Diphenoxo-Bridged NiIILnIII Dinuclear Complexes as Platforms for Heterotrimetallic (LnIIINiII)2RuIII Systems with a High-Magnetic-Moment Ground State…
2012
The first examples of pentanuclear heterotrimetallic [(LnNi)(2)Ru] [Ln(3+) = Gd (1) and Dy (2)] complexes were prepared and magnetostructurally characterized. They exhibit ferromagnetic interactions, leading to a high-magnetic-moment ground state.
Mononuclear Complexes of Iron(II) Based on Symmetrical Tripodand Ligands: Novel Parent Systems for the Development of New Spin Crossover Metallomesog…
2011
The synthesis and characterization of a series of mononuclear tripodand-based FeII complexes by means of Mossbauer andUV/Vis spectroscopic as well as magnetic methods is reported. The complexes were obtained from the reactions of FeII salt with heterocyclic aldehydes (imd = imidazole-4(5)-carboxaldehyde, py = picolinaldehyde, or 6-Mepy = 6-methylpicolinaldehyde) and a symmetric triamine [tren = tris(2-aminoethyl)amine, tame = 2,2,2-tris(aminomethyl)ethane, or tach = 1,3,5-cis,cis-cyclohexanetriamin]. Because of extreme rigidity of the capping triamine tach, the molecular structure of {Fe[tach(imd)3](BF4)2} (1) features an unprecedented tapered trigonal prismatic FeN6 polyhedron. The molecul…
Enforcement of a high-spin ground state for the first 3d heterometallic 12-metallacrown-4 complex.
2014
Cu(II)(DMF)2Cl2[12-MC(Fe(III)N(Shi))-4](DMF)4·2DMF was synthesized as the first heterometallic transition metal 12-MC-4 complex. The purposeful placement of specific metal ions in the different sites of the metallacrown attains the establishment of a high-spin ground state. Inducing the anticipated superior exchange interactions, the central Cu(II) guest ion averts the common mutual cancellation of the spins, as is observed in the corresponding homometallic compounds.
A Discrete μ 4 ‐Oxido Tetranuclear Iron(III) Cluster
2012
Reaction of a Schiff base ligand derived from salicyloyl hydrazide and diacetyl monooxime (H2L) with a triangular μ3-oxido-centered [Fe3(μ3-O)]7+ core yields a new tetranuclear iron(III) complex. FeIII4(μ4-O) crystallizes in the triclinic space group P. Structural studies reveal that this tetranuclear iron(III) complex is a new structure type of an uncharged (alkoxido)(oxido)iron(III) cluster in which the four iron(III) ions are located at the corners of a distorted tetrahedron. A study of the magnetic properties supports the presence of antiferromagnetic interactions through the central μ4-oxido ion as well as the μ2-methoxy groups present, giving an an S = 0 ground state. Mossbauer spectr…