Probing the structural features that influence the mesomorphic properties of substituted dibenz[a,c]anthracenes

• Published in: Canadian journal of chemistry Vol. 95; no. 4; pp. 399 - 409
• Main Authors: Paquette, Joseph A, Psutka, Katie M, Yardley, Colin J, Maly, Kenneth E
• Format: Journal Article
• Language: English
• Published: Ottawa NRC Research Press 01-04-2017; Canadian Science Publishing NRC Research Press
• Subjects: aromatic compounds; auto-assemblage; Bromination; Chains; Chemical synthesis; composés aromatiques; Coupling; cristaux liquides; Electrons; Esters; interactions pi; liquid crystals; Mesophase; Methods; Observations; Phases; Polycyclic aromatic hydrocarbons; self-assembly; Stability; Stacks; Substitutes; Substitution reactions; synthesis; synthèse; Temperature; π–π interactions
• DOI: 10.1139/cjc-2016-0505
• EISSN: 1480-3291
• ISSN: 0008-4042

We report the synthesis and mesophase characterization of a series of novel hexaalkoxydibenzanthracenes to probe the effect of side-chain length variation and substituents on the mesophase temperature range. A series of hexaalkoxydibenz[a,c]anthracenes (
2a
–
2i
) with varying chain lengths were prepared by Suzuki coupling of the appropriate boronate ester with the corresponding dialkoxydibromonaphthalenes, followed by oxidative cyclization. Compounds
2a
–
2i
were also brominated in the 10 and 13 positions to yield the corresponding dibromo series,
4a
–
4i
. While none of the compounds,
2a
–
2i
, exhibited columnar mesophases, all of the compounds in series
4a
–
4i
did exhibit columnar phases over broad temperature ranges. To further investigate the effect of substituents on the mesomorphic properties of hexaalkoxydibenzanthracenes, we also prepared iodo-substituted
8
, nitro-substituted
9
, and amino-substituted
10
. A comparison of the mesophase temperature range with previously reported compounds
3
–
7
shows that electron-withdrawing groups promote the formation of stable mesophases. However, our results also suggest that the substituents affect mesophase stability by participating in intermolecular contacts within the columnar stacks of the mesophase.