• Title/Summary/Keyword: Weak ligand-field

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ligand Field Analyses of Tris(biuret)chromium(Ⅲ) Chloride and Hexaureachromium(Ⅲ) Bromide

  • 박성진;오병근;박영동;이규왕
    • Bulletin of the Korean Chemical Society
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    • v.20 no.8
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    • pp.943-947
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    • 1999
  • Ligand field analyses for tris(biuret)chromium(III) chloride and hexaureachromium(III) bromide were performed and compared to understand the ligand field properties of both ligands. The optimized eσO and eπO values indicate that coordinated oxygen atom in biuret ligand is a moderate s- and strong p-donor, while that in urea ligand is a weak σ- and moderate π-donor. The electronic structures of those two complexes are quite different and they were well accounted by inclusion of an anisotropic p bonding.

Luminescence, Excitation and Far-infrared Spectroscopy of cis-$\alpha$-Dichlorotriethyleneteraminechromium(III) Chloride

  • 최종하
    • Bulletin of the Korean Chemical Society
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    • v.19 no.5
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    • pp.575-579
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    • 1998
  • The 77 K luminescence and excitation spectra, and 298 K infrared and absorption spectra of $cis-{\Alpha}-[Cr(trien)Cl_2]Cl{\cdot}H_2O$ (trien=triethylenetetramine) have been measured. Ligand field electronic transitions due to spin-allowed and spin-forbidden are assigned. The zero-phonon line in the excitation spectrum splits into two components by $198\; cm^{-1}$, and the large $^2E_g$ splitting can be reproduced by the modern ligand field theory. It is confirmed that nitrogen atoms of the trien ligand have a strong σ-donor character, but chloride ligand has weak σ- and π -donor properties toward chromium(III) ion.

Spectroscopic Properties and Ligand Field Analysis of cis-Dinitrato(1,4,8,11-tetraazacyclotetradecane)chromium(III) Nitrate

  • 최종하
    • Bulletin of the Korean Chemical Society
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    • v.18 no.8
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    • pp.819-823
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    • 1997
  • The luminescence and photoexcitation spectra of cis-[Cr(cyclam)(NO3)2]NO3·½ H2O (cyclam=1,4,8,11-tetraazacyclotetradecane) taken at 77 K are reported. The infrared and visible spectra at room-temperature are also measured. The vibrational intervals of the electronic ground state are extracted from the far-infrared and emission spectra. The ten electronic bands due to spin-allowed and spin-forbidden transitions are assigned. With observed transitions, a ligand field analysis has been performed to determine the bonding property of nitrate group in the chromium(Ⅲ) complex. According to the results, it is found that nitrate ligand has weak σ- and π-donor properties toward chromium(Ⅲ).

Electronic Spectroscopy and Ligand Field Analysis of cis-$>[Cr(cycb)Cl_2]$Cl

  • Choi, Jong-Ha;Oh, In-Gyung;Subodh Kumar;Ryoo, Keon-Sang
    • Journal of Photoscience
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    • v.11 no.1
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    • pp.19-23
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    • 2004
  • The sharp-line absorption spectrum of microcrystalline samples of cis-[Cr(cycb)$Cl_2$]Cl (cycb=rac-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane) has been measured between 13000 and $16000 cm^{-1}$ at temperatures down to 5K. The 77K emission and excitation spectra, and 298 K infrared and visible absorption spectra have also been measured. The nine electronic bands due to spin-allowed and spin-forbidden transitions were assigned. Using the observed transitions, a ligand field analysis has been performed to probe the ligand field properties of coordinated atoms in the title chromium(III) complex. The zero-phonon line in the sharp-line absorption spectrum splits into two components by $240 cm^{-1}$ , and the $large ^2$$_E{g}$ splitting can be reproduced by the modem ligand field theory. It is confirmed that nitrogen atoms of the macrocyclic cycb ligand have a strong $\sigma$-donor character, but chloride ligand has weak $\sigma$- nd $\pi$-donor properties toward chromium(III) ion.n.

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Electronic Spectroscopy and Ligand Field Analysis of mer-Chloro(1,2-ethanediamine)(1,5,9-triazanonane)chromium(III) Tetrachlorzincate(II)

  • Park, Jong-Ha;Park, Yu-Chul;Kim, Hag-Sung
    • Journal of Photoscience
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    • v.7 no.3
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    • pp.97-101
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    • 2000
  • The 77 K emission and excitation spectra, and 298 K infrared and absorption spectra of mer-[CrCl(en)(dpt)]ZnCl$_4$(en=1,2-diaminoethane; dpt=1,5,9-triazanonane) have been measured. Ligand field electronic transitions due to spin-allowed and spin-forbidden are assigned. The zero-phonon line in the excitation spectrum splits into two components by 151$cm^{-1}$ /, and large$^2$E$^{g}$ splitting can be reproduced by the modern ligand field theory. It is confirmed that nitrogen atoms of the en and dpt ligands have a strong $\delta$-donor character, but chloride ligand has weak $\delta$-and $\pi$-donor properties toward chromium(III) ion.

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Spectroscopic Properties and Ligand Field Analysis of trans -Dibromo(2,2-dimethyl-1,3-diaminopropane)chromium(III) Moiety

  • Choi, Jong-Ha;Oh, In-Gyung;Lim, Woo-Taik;Ryoo, Keon-Sang;Kim, Dong-Il;Park, Yu-Chul
    • Bulletin of the Korean Chemical Society
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    • v.26 no.6
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    • pp.903-908
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    • 2005
  • The sharp-line absorption and emission spectra of $(H_{13}O_6)${$trans-[Cr(Me_2tn)_2Br_2]$}$_2Br_2(ClO_4)\;(Me_2$tn = 2,2-dimethyl-1,3-diaminopropane) have been measured between 13000 $cm^{-1}$ and 16000 $cm^{-1}$ at 5 K. The 298 K infrared and visible absorption spectra have also been measured. The nine electronic bands due to spin-allowed and spin-forbidden transitions were assigned. Using observed transitions, a ligand field analysis has been performed to probe the ligand field properties of coordinated atoms in the title chromium(III) complex ion. The zero-phonon line in the sharp-line absorption spectrum splits into two components by 286 $cm^{-1}$, and the large $^2E_g$ splitting can be reproduced by the modern ligand field theory. It is confirmed that nitrogen atoms of the Me2tn ligand have a strong $\sigma$-donor character, but the bromide has weak $\sigma$- and $\pi$-donor properties toward chromium(III) ion.

OPTICAL SPECTROSCOPY AND LIGAND FIELD PARAMETERS OF CIS-DIBROMO(1,4,8,11-TETRAAZACYCLOTETRADECANE) CHROMIUM(III) BROMIDE

  • Choi, Jong-Ha
    • Journal of Photoscience
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    • v.4 no.3
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    • pp.121-125
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    • 1997
  • The 77 K emission and excitation, and room-temperature visible spectra of cis[Cr(cyclam)Br$_2$]Br (cyclam=1,4,8,11-tetraazacyclotetradecane) are reported. The mid- and far-infrared spectra at room-temperature are also measured. The vibrational intervals of the electronic ground state are extracted from the far-infrared and emission spectra. The ten electronic bands due to spin-allowed and spin-forbidden transitions are assigned. It is found that nitrogen atoms of the cyclam ligand have strong $\sigma$-donor characters, but bromide ligand has weak $\sigma$- and $\pi$-donor properties toward chromium(III) ion. The zerophonon line in the excitation spectrum splits into two components by 172 cm$^{2-}$, and the large $^2E_g$ splitting can be reproduced by the ligand field theory.

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Electronic Spectroscopy and Ligand Field Analysis of mer-[Cr(progly)(2,2-tri)]$CIO_4$

  • Park, Jong-Ha
    • Journal of Photoscience
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    • v.9 no.3
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    • pp.51-55
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    • 2002
  • The 77 K emission and excitation spectra, and 298 K infrared and absorption spectra of [Cr(progly)(2,2-tri)]CIO$_4$[progly=prolylglycinate,2,2-tri=N-(2-aminoethyl)-1,2-ethanediamine] have been measured. The vibrational intervals of the electronic ground state are extracted from emission and infrared spectra. The twelve electronic bands due to spin-allowed and spin-forbidden transitions were assigned. Using the observed electronic transitions, a ligand field analysis was performed to determine the metaligand bonding properties for the coordinated atoms. It is found that the carboxylate oxygen of the progly is a strong $\sigma$-and $\pi$-donor while the peptide nitrogen has weak $\pi$-donor property toward chromium(III) ion.

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Electronic Spectroscopy and Ligand Field Analysis of trans-[CrX2([15]aneN4)]+(X=F,CI) (trans-[CrX2([15]aneN4)]+(X=F,CI)의 전자분광학과 리간드장 해석)

  • Jong-Ha Choi;In-Gyung Oh;Sang Hak Lee;Yu Chul Park
    • Journal of the Korean Chemical Society
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    • v.47 no.2
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    • pp.109-114
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    • 2003
  • The electronic absorption spectra of trans-$[CrX_2([15]aneN_4)]ClO_4\;([15]aneN_4$=1,4,8,12-tetraazacyclopentadecane; X=F, Cl) complexes have been interpreted using the ligand field theory. An AOMX program is used to optimize the differences between the calculated and the observed positions for the spin-allowed transition bands. The crystal field theory(CFT) parameter is directly related to the angular overlap model(AOM), normalized spherical harmonic hamiltonians(NSH), and semiempirical parameters. The various ligand field parameters are discussed in terms of their chemical significances. According to the ligand field analysis, we can confirm that the fluoride ligand is a very strong ${\sigma}-$ and ${\pi}-$donor while the chloride has weak ${\sigma}-$ and ${\pi}-$donor properties toward chromium(III) ion.

Electronic Structure and Chemical Reactivity of Transition Metal Complexes (Part 16). A Spectroscopic Study on the Electronic Structure of cis-[Cr(cyclam)$Cl_2$]Cl (전이금속 착물의 전자 구조 및 화학적 반응성 (제 16 보). cis-[Cr(cyclam)$Cl_2$]Cl의 전자 구조에 관한 분광학적 연구)

  • Choi, Jong-Ha
    • Journal of the Korean Chemical Society
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    • v.39 no.7
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    • pp.501-507
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    • 1995
  • The electronic structure of cis-$[Cr(cyclam)Cl_2]Cl$ has been investigated by the emission and excitation spectroscopy at 77K, and infrared and visible spectroscopy at room temperature. The ten electronic transitions due to spin-allowed and spin-forbidden are assigned. The zero-phonon line in the excitation spectrum splits into two components by $139\;cm^{-1}$, and it can be reproduced by modern ligand field theory. According to the results of ligand field analysis, we can confirm that nitrogen atoms of the cyclam ligand have a strong ${\sigma}$-donor character, but chloride ligand has weak ${\sigma}-$ and ${\pi}-$donor properties toward chromium(III) ion.

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