Temperature- and pressure-induced proton transfer in the 1:1 adduct formed between squaric acid and 4,4'-bipyridine

D.M.S. Martins, D.S. Middlemiss, C.R. Pulham, C.C. Wilson, M.T. Weller, P.F. Henry, N. Shankland, K. Shankland

Research output: Contribution to journalArticle

66 Citations (Scopus)

Abstract

We have applied a combination of spectroscopic and diffraction methods to study the adduct formed between squaric acid and bypridine, which has been postulated to exhibit proton transfer associated with a single-crystal to single-crystal phase transition at ca. 450 K. A combination of X-ray single-crystal and very-high flux powder neutron diffraction data confirmed that a proton does transfer from the acid to the base in the high-temperature form. Powder X-ray diffraction measurements demonstrated that the transition was reversible but that a significant kinetic energy barrier must be overcome to revert to the original structure. Computational modeling is consistent with these results. Modeling also revealed that, while the proton transfer event would be strongly discouraged in the gas phase, it occurs in the solid state due to the increase in charge state of the molecular ions and their arrangement inside the lattice. The color change is attributed to a narrowing of the squaric acid to bipyridine charge-transfer energy gap. Finally, evidence for the possible existence of two further phases at high pressure is also presented.
LanguageEnglish
Pages3884-3893
Number of pages10
JournalJournal of the American Chemical Society
Volume131
Issue number11
DOIs
Publication statusPublished - 25 Mar 2009

Fingerprint

Proton transfer
Protons
Single crystals
Pressure
Temperature
Acids
Neutron Diffraction
Powder Diffraction
Neutron powder diffraction
Energy barriers
Phase Transition
Energy Transfer
X-Ray Diffraction
Kinetic energy
Powders
X ray powder diffraction
Charge transfer
Energy gap
Color
Diffraction

Keywords

  • spectroscopy
  • diffraction
  • proton transfer
  • single-crystal
  • neutron diffraction
  • squaric acid
  • bypridine

Cite this

Martins, D. M. S., Middlemiss, D. S., Pulham, C. R., Wilson, C. C., Weller, M. T., Henry, P. F., ... Shankland, K. (2009). Temperature- and pressure-induced proton transfer in the 1:1 adduct formed between squaric acid and 4,4'-bipyridine. Journal of the American Chemical Society, 131(11), 3884-3893. https://doi.org/10.1021/ja8082973
Martins, D.M.S. ; Middlemiss, D.S. ; Pulham, C.R. ; Wilson, C.C. ; Weller, M.T. ; Henry, P.F. ; Shankland, N. ; Shankland, K. / Temperature- and pressure-induced proton transfer in the 1:1 adduct formed between squaric acid and 4,4'-bipyridine. In: Journal of the American Chemical Society. 2009 ; Vol. 131, No. 11. pp. 3884-3893.
@article{d7aa924f80e948368cbabc4ca896eb5d,
title = "Temperature- and pressure-induced proton transfer in the 1:1 adduct formed between squaric acid and 4,4'-bipyridine",
abstract = "We have applied a combination of spectroscopic and diffraction methods to study the adduct formed between squaric acid and bypridine, which has been postulated to exhibit proton transfer associated with a single-crystal to single-crystal phase transition at ca. 450 K. A combination of X-ray single-crystal and very-high flux powder neutron diffraction data confirmed that a proton does transfer from the acid to the base in the high-temperature form. Powder X-ray diffraction measurements demonstrated that the transition was reversible but that a significant kinetic energy barrier must be overcome to revert to the original structure. Computational modeling is consistent with these results. Modeling also revealed that, while the proton transfer event would be strongly discouraged in the gas phase, it occurs in the solid state due to the increase in charge state of the molecular ions and their arrangement inside the lattice. The color change is attributed to a narrowing of the squaric acid to bipyridine charge-transfer energy gap. Finally, evidence for the possible existence of two further phases at high pressure is also presented.",
keywords = "spectroscopy, diffraction, proton transfer, single-crystal, neutron diffraction, squaric acid, bypridine",
author = "D.M.S. Martins and D.S. Middlemiss and C.R. Pulham and C.C. Wilson and M.T. Weller and P.F. Henry and N. Shankland and K. Shankland",
note = "Strathprints' policy is to record up to 8 authors per publication, plus any additional authors based at the University of Strathclyde. More authors may be listed on the official publication than appear in the Strathprints' record.",
year = "2009",
month = "3",
day = "25",
doi = "10.1021/ja8082973",
language = "English",
volume = "131",
pages = "3884--3893",
journal = "Journal of the American Chemical Society",
issn = "0002-7863",
publisher = "American Chemical Society",
number = "11",

}

Martins, DMS, Middlemiss, DS, Pulham, CR, Wilson, CC, Weller, MT, Henry, PF, Shankland, N & Shankland, K 2009, 'Temperature- and pressure-induced proton transfer in the 1:1 adduct formed between squaric acid and 4,4'-bipyridine' Journal of the American Chemical Society, vol. 131, no. 11, pp. 3884-3893. https://doi.org/10.1021/ja8082973

Temperature- and pressure-induced proton transfer in the 1:1 adduct formed between squaric acid and 4,4'-bipyridine. / Martins, D.M.S.; Middlemiss, D.S.; Pulham, C.R.; Wilson, C.C.; Weller, M.T.; Henry, P.F.; Shankland, N.; Shankland, K.

In: Journal of the American Chemical Society, Vol. 131, No. 11, 25.03.2009, p. 3884-3893.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Temperature- and pressure-induced proton transfer in the 1:1 adduct formed between squaric acid and 4,4'-bipyridine

AU - Martins, D.M.S.

AU - Middlemiss, D.S.

AU - Pulham, C.R.

AU - Wilson, C.C.

AU - Weller, M.T.

AU - Henry, P.F.

AU - Shankland, N.

AU - Shankland, K.

N1 - Strathprints' policy is to record up to 8 authors per publication, plus any additional authors based at the University of Strathclyde. More authors may be listed on the official publication than appear in the Strathprints' record.

PY - 2009/3/25

Y1 - 2009/3/25

N2 - We have applied a combination of spectroscopic and diffraction methods to study the adduct formed between squaric acid and bypridine, which has been postulated to exhibit proton transfer associated with a single-crystal to single-crystal phase transition at ca. 450 K. A combination of X-ray single-crystal and very-high flux powder neutron diffraction data confirmed that a proton does transfer from the acid to the base in the high-temperature form. Powder X-ray diffraction measurements demonstrated that the transition was reversible but that a significant kinetic energy barrier must be overcome to revert to the original structure. Computational modeling is consistent with these results. Modeling also revealed that, while the proton transfer event would be strongly discouraged in the gas phase, it occurs in the solid state due to the increase in charge state of the molecular ions and their arrangement inside the lattice. The color change is attributed to a narrowing of the squaric acid to bipyridine charge-transfer energy gap. Finally, evidence for the possible existence of two further phases at high pressure is also presented.

AB - We have applied a combination of spectroscopic and diffraction methods to study the adduct formed between squaric acid and bypridine, which has been postulated to exhibit proton transfer associated with a single-crystal to single-crystal phase transition at ca. 450 K. A combination of X-ray single-crystal and very-high flux powder neutron diffraction data confirmed that a proton does transfer from the acid to the base in the high-temperature form. Powder X-ray diffraction measurements demonstrated that the transition was reversible but that a significant kinetic energy barrier must be overcome to revert to the original structure. Computational modeling is consistent with these results. Modeling also revealed that, while the proton transfer event would be strongly discouraged in the gas phase, it occurs in the solid state due to the increase in charge state of the molecular ions and their arrangement inside the lattice. The color change is attributed to a narrowing of the squaric acid to bipyridine charge-transfer energy gap. Finally, evidence for the possible existence of two further phases at high pressure is also presented.

KW - spectroscopy

KW - diffraction

KW - proton transfer

KW - single-crystal

KW - neutron diffraction

KW - squaric acid

KW - bypridine

U2 - 10.1021/ja8082973

DO - 10.1021/ja8082973

M3 - Article

VL - 131

SP - 3884

EP - 3893

JO - Journal of the American Chemical Society

T2 - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

SN - 0002-7863

IS - 11

ER -