Infrared spectroscopic and computational studies on formamide solutions of Ca2+. Vibrational frequencies of formamide and modes of coordination to Ca2+

Kazuhiko Ohashi, Nobutaka Hikiishi, Hayato Takeshita

Research output: Contribution to journalArticle

Abstract

Infrared spectroscopy for formamide (FA) solutions of Ca(ClO4)2 shows that both CN stretch (νCN) and CO stretch (νCO) bands of FA undergo upshifts in the presence of Ca2+. Modeling of Ca2+ in FA solutions is accomplished by quantum chemical calculations for Ca2+(FA)n (n = 1–8) complexes with Polarizable Continuum Model (PCM). The calculations indicate that bidentate Ca2+(FA)4 complexes are not consistent with the observed upshift of the νCN band, although a bidentate coordination of four FA molecules via both O and N atoms was assumed in a previous study of the same system. The experimental results are reasonably reproduced by adopting Ca2+(FA)7 and Ca2+(FA)8 complexes with a monodentate coordination of all FA molecules via the O atom. A strong coupling among the CO oscillators is shown to be responsible for the upshifts of the νCO modes despite the O atom coordination.

LanguageEnglish
Pages112-119
Number of pages8
JournalSpectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy
Volume206
DOIs
Publication statusPublished - Jan 5 2019

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Vibrational spectra
Infrared radiation
Atoms
atoms
Molecules
molecules
Infrared spectroscopy
infrared spectroscopy
oscillators
continuums

All Science Journal Classification (ASJC) codes

  • Analytical Chemistry
  • Atomic and Molecular Physics, and Optics
  • Instrumentation
  • Spectroscopy

Cite this

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title = "Infrared spectroscopic and computational studies on formamide solutions of Ca2+. Vibrational frequencies of formamide and modes of coordination to Ca2+",
abstract = "Infrared spectroscopy for formamide (FA) solutions of Ca(ClO4)2 shows that both CN stretch (νCN) and CO stretch (νCO) bands of FA undergo upshifts in the presence of Ca2+. Modeling of Ca2+ in FA solutions is accomplished by quantum chemical calculations for Ca2+(FA)n (n = 1–8) complexes with Polarizable Continuum Model (PCM). The calculations indicate that bidentate Ca2+(FA)4 complexes are not consistent with the observed upshift of the νCN band, although a bidentate coordination of four FA molecules via both O and N atoms was assumed in a previous study of the same system. The experimental results are reasonably reproduced by adopting Ca2+(FA)7 and Ca2+(FA)8 complexes with a monodentate coordination of all FA molecules via the O atom. A strong coupling among the CO oscillators is shown to be responsible for the upshifts of the νCO modes despite the O atom coordination.",
author = "Kazuhiko Ohashi and Nobutaka Hikiishi and Hayato Takeshita",
year = "2019",
month = "1",
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doi = "10.1016/j.saa.2018.07.089",
language = "English",
volume = "206",
pages = "112--119",
journal = "Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy",
issn = "1386-1425",
publisher = "Elsevier",

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TY - JOUR

T1 - Infrared spectroscopic and computational studies on formamide solutions of Ca2+. Vibrational frequencies of formamide and modes of coordination to Ca2+

AU - Ohashi, Kazuhiko

AU - Hikiishi, Nobutaka

AU - Takeshita, Hayato

PY - 2019/1/5

Y1 - 2019/1/5

N2 - Infrared spectroscopy for formamide (FA) solutions of Ca(ClO4)2 shows that both CN stretch (νCN) and CO stretch (νCO) bands of FA undergo upshifts in the presence of Ca2+. Modeling of Ca2+ in FA solutions is accomplished by quantum chemical calculations for Ca2+(FA)n (n = 1–8) complexes with Polarizable Continuum Model (PCM). The calculations indicate that bidentate Ca2+(FA)4 complexes are not consistent with the observed upshift of the νCN band, although a bidentate coordination of four FA molecules via both O and N atoms was assumed in a previous study of the same system. The experimental results are reasonably reproduced by adopting Ca2+(FA)7 and Ca2+(FA)8 complexes with a monodentate coordination of all FA molecules via the O atom. A strong coupling among the CO oscillators is shown to be responsible for the upshifts of the νCO modes despite the O atom coordination.

AB - Infrared spectroscopy for formamide (FA) solutions of Ca(ClO4)2 shows that both CN stretch (νCN) and CO stretch (νCO) bands of FA undergo upshifts in the presence of Ca2+. Modeling of Ca2+ in FA solutions is accomplished by quantum chemical calculations for Ca2+(FA)n (n = 1–8) complexes with Polarizable Continuum Model (PCM). The calculations indicate that bidentate Ca2+(FA)4 complexes are not consistent with the observed upshift of the νCN band, although a bidentate coordination of four FA molecules via both O and N atoms was assumed in a previous study of the same system. The experimental results are reasonably reproduced by adopting Ca2+(FA)7 and Ca2+(FA)8 complexes with a monodentate coordination of all FA molecules via the O atom. A strong coupling among the CO oscillators is shown to be responsible for the upshifts of the νCO modes despite the O atom coordination.

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JO - Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy

T2 - Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy

JF - Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy

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