title: Excimer formation in a confined space: photophysics of ladderphanes with tetraarylethylene linkers.
abstract: Communication between chromophores is vital for both natural and non-natural photophysical processes. Spatial confinements offer unique conditions to scrutinize such interactions. Polynorbornene- and polycyclobutene-based ladderphanes are ideal model compounds in which all tetraarylethylene (TAE) linkers are aligned coherently. The spans for each of the monomeric units in these ladderphanes are 4.5-5.5 Å. Monomers do not exhibit emission, because bond rotation in TAE can quench the excited-state energy. However, polymers emit at 493 nm (Φ=0.015) with large Stokes shift under ambient conditions and exhibit dual emission at 450 and 493 nm at 150 K. When the temperature is lowered, the emission intensity at 450 nm increases, whereas that at 493 nm decreases. At 100 K, both monomers and polymers emit only at 450 nm. This shorter-wavelength emission arises from the intrinsic emission of TAE chromophore, and the emission at 493 nm could be attributed to the excimer emission in the confined space of ladderphanes. The fast kinetics suggest diffusion-controlled formation of the excimer.
authors.affiliation: Department of Chemistry, National Taiwan University, Taipei, 106 (Taiwan); Department of Chemical Engineering, Feng Chia University, Taichung, 407 (Taiwan).
authors.forename: Chih-Hsien
authors.initials: CH
authors.lastname: Chen
authors.forename: Kamani
authors.initials: K
authors.lastname: Satyanarayana
authors.forename: Yi-Hung
authors.initials: YH
authors.lastname: Liu
authors.forename: Shou-Ling
authors.initials: SL
authors.lastname: Huang
authors.forename: Tsong-Shin
authors.initials: TS
authors.lastname: Lim
authors.forename: Tien-Yau
authors.initials: TY
authors.lastname: Luh
mesh_terms: D003503:Cyclobutanes / Q000737:chemistry*; D004058:Diffusion; D005030:Ethylenes / Q000737:chemistry*; D007700:Kinetics; D010969:Plastics / Q000737:chemistry*; D058105:Polymerization
chemical_list: D003503:Cyclobutanes; D005030:Ethylenes; D010969:Plastics; C071464:polynorbornen
keywords: confinement; excimers; ladderphanes; photophysics; ring-opening polymerization