Competition between Methoxy-Based and Pyrazine-Based Synthons in Methoxy-Substituted Distyrylpyrazines

Abstract

Four new methoxy-substituted derivatives of E,E-2,5-bis(2-phenylethenyl)pyrazine have been synthesized. The supramolecular structures of the resulting set of five polymorphs have been studied using single-crystal X-ray diffraction to gauge the influence of the position of the methoxy groups on the organization of the molecules in the solid state, as part of an attempt to dispense with the particular polymorphism of the parent compound. The crystal packing patterns were analyzed in terms of the two pyrazine-based synthons found in the parent compound's crystal structure, the π pyrazine 3 3 3 π phenyl stacking synthon, and the pyrazine hydrogen-bonded synthon, as well as in terms of weak intermolecular interactions such as CH 3 3 3 O, CH 3 3 3 N, and CH 3 3 3 π. The analysis shows that the introduction of methoxy groups in positions other than only the para position of the peripheral benzene rings successfully switches off the two synthons seen in the parent compound and that the new compounds adopt other packing strategies, based on methoxy 3 3 3 methoxy and -OCH 3 3 3 3 π contacts. Polymorphism, however, remains.

Effect of substituents on crystal packing of functionalized 4,4′-bis(benzylideneamino)diphenyl ether(s) and their reduced benzyl forms: Synthesis, characterization, optical and thermal properties

“…Because of these effects CHÁ Á Áp stacking becomes increasingly unlikely, thus switching off the CHÁ Á Áp interactions. In fact, each AOCH 3 groups of non-centrosymmetric molecule form two C14AH14CÁ Á ÁO2 donor-acceptor contacts and link two molecules along the b-axis with the H14CÁ Á ÁO2 distance of 2.574 Å which is in good agreement with the similar interactions reported in literature [12]. Interestingly, the C14AH14CÁ Á ÁO2 donor-acceptor groups of the linked molecules connect another set of two molecules along c-axis in a trans manner and thereby aligned the incoming molecules parallel to the non-centrosymmetric molecule along c-axis with intermolecular spacing of $3.087 Å.…”

“…3c and d. This tendency of AOCH 3 group of 2 to favor helical contacts is unprecedented. However, AOCH 3 groups are known to favor reciprocal contacts among each other in the crystal structures of methoxy-substituted distryrylbenzenes [12,28].…”

“…Supramolecular structures of several organic molecules and their properties are clearly shown to be sustained via hydrogen bonds and pÁ Á Áp interactions. For instance, a clear analogy between the structures and polymorphs of methoxy-substituted distyrylpyrazines has been emerging from a detailed comparison of their supramolecular structures stabilized via CAHÁ Á ÁO, pÁ Á Áp and CAHÁ Á ÁN interactions [12]. It is clear that favorable non-covalent interactions between organic molecules include pÁ Á Áp and CAHÁ Á Áp interactions, nevertheless, both types of interactions appeared to be a subject of the electronic nature of substituents [13].…”

Effects of Catalyst Pore Structure and Acid Properties on the Dehydration of Glycerol

“…In recent years, the design and synthesis of metal‐organic coordination complexes are of continuous interest not only for their interesting molecular topologies1,2 but also for their potential applications in chemical engineering, chemistry, and materials science including gas storage, luminescent, conductive material, and DNA binding 3–7. Nitrogen ligands, particularly in the form of N‐heterocycles, have been widely used in the construction of coordination complexes 8,9. Among the N‐containing ligands, 4, 4′‐bipyridine (bpy) is an excellent neutral linear ligand in the construction of metal‐organic coordination complexes.…”

Short Intramolecular O···O Contact in Someo-Dialkoxybenzene Derivatives Generates Efficient Hydrogen Bonding Acceptor Area

“…3,[6][7][8][9] It is of special interest for supramolecular studies to understand and predict the preferred contacts of those structural fragments, which frequently appear as 4 components of the important natural and synthetic products. The fragment presented in Figure 1 is common for a number of compounds with interesting structural features, [10][11][12][13][14][15] different natural products with biological activity (papaverine, dopamine, veratrole, glaucine, vanillin) 16,17 , a number of synthetic drugs [18][19][20] , as well as of host materials based on crown ethers. [21][22][23] Regardless the general abundance of the o-dialkoxybenzene fragment, to our knowledge, no systematic study of its solid state structural properties or the potential role in supramolecular arrangement has been performed.…”