Excited state dynamics and structures of functionalized phthalocyanines. 1. Self-regulated assembly of zinc helicenocyanine

Lin X. Chen*, George B. Shaw, David M. Tiede, Xiaobing Zuo, Peter Zapol, Paul C. Redfern, Larry A. Curtiss, Thanasat Sooksimuang, Braja K. Mandal

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

16 Scopus citations

Abstract

Recently synthesized zinc helicenocyanine (ZnHc), where four helicene groups are fused with a phthalocyanine (Pc) core through all-carbon linkages, exhibits an unusually strong tendency of forming soluble molecular aggregates in organic solvents. The aggregation results in a strong optical absorption across most of the visible region, which is drastically different from that of its monomer. The aggregation is suppressed by dissolving ZnHc in a liquid crystal, octylbiphenylcarbonitrile (OBCN), where the monomer ZnHc dominates and exhibits a typical optical absorption spectrum of monomeric zinc phthalocyanine, except red shift in both Q- and B- bands due to π-conjugation expansion. This study correlates optical properties and excited state dynamics of ZnHc with intra- and intermolecular electronic interactions, using quantum mechanical calculations and ultrafast transient absorption spectroscopy. Structural details of the aggregates are revealed by small-angle X-ray scattering (SAXS) to be uniformly dimers with alkoxy chains wrapped around the core of a face-to-face dimer. The results suggest that while the peripheral helicene moieties in ZnHc are electronically coupled to the Pc core via expansion of the π-conjugation of the macrocycle, the coupling is attenuated by the "lock washer" conformation of the nonplanar peripheral helicenes which prevents π-conjugation throughout the entire macrocycle. The interplay between π-conjugation expansion in the macrocyle plane and the π-π stacking out of the macrocyle plane produces a structure that facilitates the unique optical properties and self-regulated assembly into nanoscale structures in solution. These novel optical properties are explored for potential applications in various areas.

Original languageEnglish (US)
Pages (from-to)16598-16609
Number of pages12
JournalJournal of Physical Chemistry B
Volume109
Issue number35
DOIs
StatePublished - Sep 8 2005

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

Fingerprint Dive into the research topics of 'Excited state dynamics and structures of functionalized phthalocyanines. 1. Self-regulated assembly of zinc helicenocyanine'. Together they form a unique fingerprint.

Cite this