Crystal engineered acid-base complexes with 2d and 3d hydrogen bonding systems using p-hydroxybenzoic acid as the building block

• Published in: Journal of the Serbian Chemical Society 2010-01, Vol.75 (4), p.459-473
• Main Authors: Zhao, Pu, Wang, Xian, Jian, Fang, Zhang, Jun, Xiao, Lian
• Format: Article
• Language: English
• Subjects: crystal structure; hydrogen bonding; p-hydroxybenzoic acid; supramolecular
• ISSN: 0352-5139; 1820-7421
• DOI: 10.2298/JSC090416011Z

p-Hydroxybenzoic acid (p-HOBA) was selected as the building block for self-assembly with five bases, i.e., diethylamine, tert-butyl amine, cyclohexylamine, imidazole and piperazine, and generate the corresponding acid-base complexes 1-5. Crystal structure analyses suggest that proton-transfer from the carboxyl hydrogen to the nitrogen atom of the bases can be observed in 1-4; while only in 5 does a solvent water molecule co-exists with p-HOBA and piperazine. With the presence of O-H?O hydrogen bonds in 1-4, the deprotonated p-hydroxybenzoate anions (p-HOBAA-) are simply connected each other in a head-to-tail motif to form one-dimensional (1D) arrays, which are further extended to distinct two-dimensional (2D) (for 1 and 4) and three-dimensional (3D) (for 2 and 3 ) networks via N-H?O interactions. While in 5, neutral acid and base are combined pair wise by O-H?N and N-H?O bonds to form a 1D tape and then the 1D tapes are sequentially combined by water molecules to create a 3D network. Some interlayer or intralayer C-H?O, C-H?? and ??? interactions help to stabilize the supramolecular buildings. Melting point determination analyses indicate that the five acidbase complexes are not the ordinary superposition of the reactants and they are more stable than the original reactants. p-Hidroksibenzoeva kiselina (p-HOBA) je izabrana kao element za samoizgradnju sa pet baza: dietilaminom, tert-butilaminom, cikloheksilaminom, imidazolom i piperazinom gradeci odgovarajuce kiselinsko-bazne komplekse 1-5. Kristalne-strukturne analize ukazuju da se proton-transfer sa karboksilnog vodonika na azotov atom baze moze uociti kod 1-4, a samo u 5, rastvarac molekula vode koegzistira sa (p-HOBA) i piperazinom. Vodonicnim vezama O-H?O prisutnim u 1- 4, deprotonovani p-hidroksibenzoevi anjoni (p-HOBAA-) se jednostavno povezuju motivom glava-na-rep gradeci jednodimenionalne (1D) nizove dodatno prosirene na razne dvo-dimenzionalne (2D) (za 1 i 4) i trodimenzionalne (3D)(za 2 i 3) putem mreze N-H?O interakcija. Dok su u 5 neutralna kiselina i baza povezane parovima O-H?N i N-H?O veza gradeci 1D traku, kombinacijom 1D traka sa molekulima vode kreira se 3D mreza. Neke C-H?O, C-H? ? i ??? interakcije ivan i unutar slojeva pomazu stabilizovanju supramolekularnih tvorevina. Tacke topljenja ukazuju da 5 kiselinsko-baznih kompleksa nisu obicna superpozicija reaktanata i da su stabilniji od originalnih reaktanata.