Multi-component crystals of 4-phenylpyridine: challenging the boundaries between co-crystal and organic salt formation with insight into solid-state proton transfer

Abstract

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Studies on the synthesis, structural characterization, Hirshfeld analysis and stability of apovincamine (API) and its co-crystal (terephthalic acid: Apovincamine=1:2)

“…Traditionally focusing on salt formation [4], the formation of co-crystals has recently been developed as a potential alternative http with some of the produced co-crystals shown to display unique properties. In general, pharmaceutical co-crystals [5] are defined as multi-component crystalline structures composed of an active pharmaceutical ingredient (API) and co-crystal forming components that are solid at ambient conditions and bound via non-covalent interactions [6].…”

Living in the salt-cocrystal continuum: indecisive organic complexes with thermochromic behaviour

“…In general, within the salt-cocrystal continuum a molecular complex of given stoichiometry will adopt a single protonation state under all conditions. There are examples of protonation state varying with stoichiometry, [22][23][24][25] but it is uncommon for multiple protonation states to be accessible under ambient conditions for the same stoichiometry. There is a potential analogy here with concomitant polymorphism, i.e.…”

Assessment of Co-sublimation for the Formation of Multicomponent Crystals

“…The combination of gallic acid and 4-phenylpyridine is known to form a 1:1 salt ( 15 , CSD refcode: TICZIQ) . Salt 15 can easily be made by liquid-assisted grinding, but in this case, GA degradation entirely prevents formation of 15 by co-sublimation.…”