Computational studies on cyclic [n]paraphenyleneacetylenes using homodesmotic reactions

Mohamad Akbar Ali, Mangala Sunder Krishnan

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13 Scopus citations


Cyclic [n]paraphenyleneacetylenes ([n]CPPAs) are potentially useful compounds for molecular electronics. In this article, a homodesmotic reaction scheme coupled with density functional theory has been used to estimate theoretically strain energies and heats of formation of [n]CPPAs. Calculations have been done for a series of [n]CPPAs, containing up to ten phenylacetylene units. Strain energies of [n]CPPAs decrease, while heats of formation increase steadily with the increase in the number of phenylacetylene units using homodesmotic reaction schemes. B3LYP and mPW1PW91 functionals have been used with the Pople basis set 6-31G* to analyze the trends. The results are sensitive to the scheme of homodesmotic reaction chosen, thereby necessitating careful chemical consideration before spending considerable computational resources for higher [n]CPPAs not considered here. Computational estimates for the ring diameter of [n]CPPAs and absolute entropy have also been obtained here. The HOMO-LUMO gaps of the belt shaped [n]CPPAs show an odd-even difference. In addition, the HOMOs of the [3]CPPA, [5]CPPA, [7]CPPA and [9]CPPA are doubly degenerate.

Original languageBritish English
Pages (from-to)2149-2158
Number of pages10
JournalMolecular Physics
Issue number20
StatePublished - 2009


  • Cyclic [n]paraphenyleneacetylenes
  • Density functional theory
  • Electronic properties
  • Heats of formation
  • Homodesmotic reactions
  • Strain energies


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