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A series of molecular complexes of the proton sponge 1,8-bis(dimethylamino)naphthalene (DMAN) with mono-substituted halobenzoic acids are reported, illustrating the designed exploitation of the characteristics of the proton sponge to induce short, charge-assisted hydrogen bonds in a predictable and reproducible manner. In every case, a DMAN molecule extracts a proton from the carboxylic acid group of the benzoic acid, as a result of which a recurrent supramolecular unit between a neutral and a 2 deprotonated benzoic acid molecule is formed featuring an extremely short, strong O-H···O hydrogen bond, within a predominant crystallisation ratio of 1:2 (DMAN:benzoic acid). KEYWORDS (Word Style "BG_Keywords"). If you are submitting your paper to a journal that requires keywords, provide significant keywords to aid the reader in literature retrieval.

4-Phenoxyphenol is a simple organic molecule that crystallizes as a porous material with channels running throughout the structure. The channels are constructed by a 6-fold hydrogen bonded ring and can host solvent molecules incorporated during crystal growth, with a minimum channel diameter of 5.8−5.9 Å; each channel usually contains a single solvent molecule per unit cell. The hydrogen bonded ring shows surprising flexibility, being able both to breathe and to sustain its crystalline integrity even when grown with empty pores. This is particularly surprising given that the remainder of the interactions within the crystal structure are C−H•••π interactions and are weak in nature. It is also possible to grow "dry" porous 4-phenoxyphenol crystals by using a bulky solvent in the recrystallization.

Proton behavior within the hydrogen bond (HB) networks of five molecular complexes of the proton sponge DMAN and different organic acids is investigated by single crystal neutron diffraction. The complexes form with either 2:1 (acid:DMAN) or 1:1 stoichiometric ratios and contain common structural motifs. All show proton transfer from an acid to DMAN forming a DMANH + moiety and hydrogen bonded acid dimers; complexes with halobenzoic acids have acid molecules linked by short, strong, charge-assisted HBs, while all complexes contain a short, strong, intramolecular N-H•••N HB in DMANH +. The hydrogen atom behavior within the short, strong HBs, accurately described from the neutron data, is rationalized in terms of weak interactions in the local crystal environment, with the position of the proton within both sets of short, strong HBs affected by a combination of the weak interactions in the vicinity of the HBs. A correlation is also found between the thermal motion of the bound proton in the N-H•••N HB of DMANH + and nearby oxygen atoms when they are sufficiently close to one another. This work shows that all interactions in the local environment combine to determine the behavior of protons within short, strong HBs and that by taking these interactions into account further control over the crystal structure and properties may be achievable.