Pressure-preferred symmetric reactions of 4,4′-bipyridine hydrobromide

Michalina Anioła,Andrzej Katrusiak

doi:10.1039/c6ce00356g

Michalina Anioła, Andrzej Katrusiak

Open Access

https://doi.org/10.1039/c6ce00356g

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Journal: CrystEngComm	Publication Date: Jan 1, 2016
Citations: 5	License type: cc-by

Affiliation: Adam Mickiewicz University in Poznań

Abstract

High pressure and temperature trigger symmetric chemical reactions of 4,4′-bipyridine hydrobromide monohydrate (44′biPyHBr·H2O) in methanol solution. Above 0.1 GPa and 423 K, the 4,4′-bipyridinium dibromide salt (44′biPy2HBr) precipitates, while the 4,4′-bipyridine free base remains dissolved in the methanol–water mixture. At 0.35 GPa and 473 K, both pyridine moieties are N-methylated and N,N-dimethylbipyridinium dibromide (44′biPy2CH3Br) is formed. None of the high-pressure compounds of 44′biPy2HBr and 44′bPy2CH3Br are solvated, which contrasts with the strong preference of analogous 1,4-diazabicyclo[2.2.2]octane (dabco) monosalts and disalts to form solvates at high-pressure. The high-pressure reactivity of 44′biPyHBr is analogous to that of 1,4-diazabicyclo[2.2.2]octane hydrobromide (dabcoHBr); however, dabcoHBr is asymmetrically N-methylated at one amine site only. This asymmetric mono N-methylation of dabcoHBr has been associated with strong electrostatic interactions between the transannular N-atoms.

Highlights

High-pressure can drastically change the reactivity of chemical compounds and their properties.[1]
0.1 GPa and 423 K, the 4,4′-bipyridinium dibromide salt (44′biPy2HBr) precipitates, while the 4,4′-bipyridine free base remains dissolved in the methanol–water mixture
It was previously established that the isothermal or isochoric recrystallizations of 44′biPyHBr∙H2O from methanol solution below 0.55 GPa and 353 K retain the ambient-pressure orthorhombic phase α, while recrystallizations above 0.55 GPa lead to the monoclinic β phase

Summary

Michalina Anioła and Andrzej Katrusiak*

High pressure and temperature trigger symmetric chemical reactions of 4,4′-bipyridine hydrobromide monohydrate (44′biPyHBr·H2O) in methanol solution. 0.1 GPa and 423 K, the 4,4′-bipyridinium dibromide salt (44′biPy2HBr) precipitates, while the 4,4′-bipyridine free base remains dissolved in the methanol–water mixture. At 0.35 GPa and 473 K, both pyridine moieties are N-methylated and N,Ndimethylbipyridinium dibromide (44′biPy2CH3Br) is formed. None of the high-pressure compounds of 44′biPy2HBr and 44′bPy2CH3Br are solvated, which contrasts with the strong preference of analogous 1,4-diazabicyclo[2.2.2]octane (dabco) monosalts and disalts to form solvates at high-pressure. The highpressure reactivity of 44′biPyHBr is analogous to that of 1,4-diazabicyclo[2.2.2]octane hydrobromide (dabcoHBr); dabcoHBr is asymmetrically N-methylated at one amine site only. This asymmetric mono N-methylation of dabcoHBr has been associated with strong electrostatic interactions between the transannular N-atoms

Introduction

Discussion