Tris-Azo Triangular Paraphenylenes: Synthesis and Reversible Interconversion into Radial π-Conjugated Macrocycles

10 January 2024, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

We report the synthesis of cycloparaphenylene derivatives featuring tris-azo groups. The smaller derivative, [3]cycloazobenzene ([3]CAB-0), adopts a triangular all-cis form and exhibits thermally and photochemically stable characteristics due to significant ring strain, as well as symmetric Kagome-patterned crystal packing. In contrast, the as-synthesized [3]cycloazobenzene with three biphenylene bridges ([3]CAB-1) adopts a similar triangular all-cis form; however, it undergoes photoinduced isomerization, leading to a mixture of cis and trans forms at a photostationary state. Interestingly, the addition of an excess of acid selectively leads to the formation of the all-trans form. DFT calculations reveal that the interconversion from a triangular to a circular shape correlates with an increase in HOMO and a decrease in LUMO, characteristics intrinsic to radial π-conjugated systems.

Keywords

Cycloparaphenylene
Azobenzene
Cis-trans isomerization
Molecular triangles
Radial π-conjugation

Supplementary materials

Title
Description
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Title
Supporting Information
Description
Experimental procedure, Spectroscopic data, Computational details
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Title
cif file of [3]CAB-0
Description
cif file of [3]CAB-0
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cif file of [3]CAB-1
Description
cif file of [3]CAB-1
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