Imidazole base was crystallized with different aromatic carboxylic acids 2,4-dihydroxybenzoic acid, 5-chlorosalicylic acid, and 1,8-naphthalic acid, affording three new binary molecular organic salts of [(C 3 H 5 N 2 + )·(C 7 H 5 O 4 )] (1), [(C 3 H 5 N 2 + )·(C 7 H 4 O 3 Cl )] C 7 H 5 O 3 Cl (2), and [(C 3 H 5 N 2 + ) (C 12 H 7 O 4 )] (3). Proton transfer occurs from the COOH of carboxylic acid to nitrogen of imidazole in all complexes (1-3), leading to the hydrogen bond N-H…O in all structures. To our knowledge, the recognition pattern between the carboxylic acid group and imidazole (acid-imidazole synthon) is less well-studied so far. The cooperation among COOH, COO and imidazolium cation functional groups for the observed hydrogen bond synthons is examined in the three structures. Generally, the strong N-H…O and O-H…O hydrogen bonds define supramolecular architecture and connectivity within chains, while weaker C-H…O hydrogen bonds play the dominant role in controlling the interactions between layers in these novel organic salts. Thermal stability of these compounds has been investigated by thermogravimetric analysis (TGA) of mass loss.
WANG LeiZHAO LeiLIU MengCHEN RuiXinYANG YuGU YuanXiang
Four hydroxybenzoic acid building blocks, m-hydroxybenzoic acid, 2,4-dihydroxybenzoic acid, 2,5-dihydroxyterephthalic acid, and 5-hydroxyisophthalic acid, have been synthesized as robust cocrystallizing agents and employed in reactions with piperazine, including [（C4H12N2 2＋）.（C7H5O3-）2] （l）, [（CaH12N2 2＋）.（C7H5O4-）2] （2）, [（C4H12N2 2＋）.（C8H5O6 2- ）] （3）, and [（C4H12N2 2＋）1/2. （C8H5O5）] . 2H2O （4）. Hydrogen-bonded directed assemblies of four salts were validated by single-crystal X-ray diffraction analysis. In compounds 1-4, hydroxybenzoic acids are all deprotonated and piperazine molecules are all protonated to form piperazine dications and keep the chair conformation. Thermal stability of these compounds has been investigated.
WANG LeiXUE RuiFengXU LingYanLU XiFengCHEN RuiXinTAO XuTang
A layered zirconogermanate, （H2DETA）[ZrGe3O8F2]（1）, was hydro（solvo）thermally synthesized with diethylenetriamine（DETA） as template, and structurally determined by X-ray single-crystal diffraction. Compound 1 crystallized in the monoclinic space group P21/c with data of unit cell： a=0.7644（2） nm, b=1.1235（2） nm, c=1.6860（3） nm, V=1.4479（5） nm^3,/a（Mo Ka）=6.931 mm^-1, Z=4, R1=0.0402 for 3236 reflections with Fo〉2σ（Fo）. The structure of compound I was formed by alternatively packing the inorganic layer of ZrGe3O8F2 and H2DETA templated molecules along （001） direction. It was worth pointing out that the odd bifurcated 7MR nets were surrounded by odd 3MR. The protonated and disordered H2DETA cations not only balanced the superfluous charges of framework but also stabilized the structure of compound 1 by the hydrogen bond between -NH3 group and oxygen on the framework. Furthermore, IR and TG were utilized to characterize the structure and thermal stability, respectively.
LI Ya-fengSUN Jin-xuWU Lei-leiTIAN YongWANG Dao-wuZHANG LongWANG Lei
Multifunctional molecules are capable of assembling via different supramolecular synthons, or hydrogen bond motifs, between the same or different functional groups, leading to the possibility of cocrystal. Utilization of the interplay of dimensionality （I-D, 2-D and 3-D）, orientation of functional groups of the building blocks, influence of rigid/flexible linking groups, and weak interactions provides an interesting route for the creation of novel supramolecular architectures in the crystal lattice. N-unsubstituted 1H-benzotriazole and carboxylic acid, being self-complementary molecules, offer a broad scope of study of binary compounds based on the complementary combination of H-bonding/donating sites. We report here the construction of three extended molecular networks in cocrystals of the carboxylic acid group of the acid and the 1H-benzotriazole triazole moiety. We have been able to identify four major supramolecualr synthons that would be helpful in the prediction of structural motifs for these kinds of studies. Interestingly, these heterosynthons are strikingly similar, to those of the homosynthons of the individual functional groups. The nature of the aza groups helps to enhance the overall volume of the crystal lattice thus lead- ing to the formation of various supramolecular assemblies. Thermal stability of these compounds has been investigated by thermogravimetric analysis （TGA） of mass loss.
WANG LeiZHAO LeiXUE RuiYuLU XiFengWEN YongHongYANG Yu
The two-component solid forms involving 4,4'-methylene-bis(benzenamine) included both salts and co-crystals,while 4,4'methylene-bis(benzenamine) crystallized exclusively as a salt,in agreement with the differences in the pK a values.Many of the crystal structures displayed either the neutral or the ionic form of the carboxylic acid-amino heterosynthon,and the similarity in crystal structures between the neutral and the ionized molecules makes the visual distinction between a salt and co-crystal dependent on the experimental location of the acidic proton.A variety of supramolecular hydrogen bonded motifs involving interactions between the aza molecules and carboxylic acid groups are observed rather than just the O-H···N/O-H···O motif.The motifs are identical in all the two compounds analyzed showing the robustness of these supramolecular synthons.In all adducts,recognition between the constituents is established through either N-H···O and/or O-H···O/O-H···N pairwise hydrogen bonds.In all adducts,COOH functional groups available on 1 and 2 interact with the N-donor compounds.The COOH moieties in 1 forms only single N-H···O hydrogen bonds,whereas in 2,it forms pairwise O-H···N/N-H···O hydrogen bonds.The supramolecular architectures are elegant and simple,with stacking of networks in 2,but a rather complex network with a threefold interpenetration pattern was found in 1.Thermal stability of these compounds has been investigated by thermogravimetric analysis(TGA) of mass loss.
WANG LeiZHAO LeiLIU MengLIU FaQianXIAO QiangHU ZhiQiang
The results of crystallographic analyses on 1：1 and 1：4 well-defined co-crystals formed between glycine anhydride and each of 4-hydroxybenzoic acid and 3,5-dihydroxybenzoic acid are described. Neutral molecules are connected via heteromeric O-H.-.O and N-H…O contacts leading to different packing arrangements of supramolecular chains. On the basis of the molec- ular structures of glycine anhydride and carboxylic acid guests, the hydrogen bonds are arranged to give centrosymmetric synthons V and VII which are noteworthy for their robustness. Hydrogen-bond interactions between glycine anhydride and aromatic acid provide sufficient driving force to direct molecular recognition and crystal packing. Utilization of the orientation of functional groups of the building blocks, the acidity, and weak interactions provides a route for the creation of novel supra- molecular architectures in the crystal lattice. Both two co-crystals contain the expected hydrogen-bonded motifs, and there has been no proton transfer from either of the two carboxylic acids to the aza compound moiety. This demonstrates that glycine anhydride is very capable of affecting the construction of binary co-crystals in a predictable and rationale manner. It is noted that synthons Ⅷ and IX are fairly large, but the real challenge in crystal engineering is to find a big enough synthon that occurs often enough. Thermal stability of these compounds has been investigated by thermogravimetric analysis （TGA） of mass loss.
WANG LeiZHAO LeiLIU WeiMingCHEN RuiXinGU YuanXiangYANG Yu
