Novel nanoscale 'molecular wires' and macrocyclic molecular sensors.

摘要

Due to the potential applications of the artificial arrays in photonic/electronic devices and selective molecular sensing, the investigation of photoluminescent and/or redox-active supramolecular systems, including the molecular rods and macrocyclic receptors, have attracted recent attentions. Such systems serve as the models for the practical investigation of the parameters and factors that control the processes such as electronic communication, electron/energy transfer, and host-guest interaction.; The synthesis, characterization, investigation of ground state and excited state properties have been carried out for a new series of monomeric and bimetallic molecular rods [Cl(bpy)₂M(C_nP₂)](PF ₆) and [Cl(bpy)₂M(C_nP₂)M ′(bpy)₂Cl](PF₆)₂ (M, M ′ = Os or Ru; n = 2 or 4; C₂P₂ = Ph₂P-C≡C-PPh₂, C₄P₂ = Ph₂P-C≡C-C≡C-PPh₂). Electronic communication through polyphosphine/polyyne spacers was found to decrease upon increase of the carbon chain length. Fast energy transfer from RuII-based donor to OsII-based acceptor occurs within the heterobimetallic complexes via a Dexter-type mechanism and an attenuation factor (β) of 0.02 Å−1.; Novel emissive macrocyclic receptors with PdII, Pt II, ReI, OsII or RuII metal moieties and C_nP₂ (n = 2 or 4) or C₄Ph_nP₂ (n = 1 or 2) spacers have also been successfully synthesized and characterized, as well as their monomeric precursors. Strong electronic interaction was observed between two Os II(tpy)Cl units bridged by two C₄P₂ spacers, while electronic communication between two RuII(tpy)Cl units was smaller. When the spacer goes longer as C₄PhP ₂, the electronic interaction is totally blocked. For dimeric [M(dppm)(C₂P₂)]₂(OTf)₄ (M = Pd or Pt), when the solvent polarity increases, solvatochromic absorption band shifts to higher energy, emission maximum shifts to lower energy, and quantum yield decreases. High quantum yields of 0.25 and 0.17 were observed for Os(bpy)₂(C₂P₂) ₂(PF₆)₂ and {lcub}[Re(CO)₃Cl]₂[Os(bpy) ₂]₂(C₂P₂)₄{rcub}(PF ₆)₄, representative of the few most emissive species reported with OsII centers. Energy transfer from the ReI(CO) ₃Cl-based donor to the OsII (bpy)₂-based acceptor and from the PtII(dppm)-based donor to the PdII(dppm)-based acceptor were also observed. The rate constants were studied using nano-, pico-, and femtosecond laser spectroscopy.; Guest inclusion and sensing studies have been performed using several above emissive metallocycles. The correlation between the guest molecule size, cavity dimension, and the host-guest binding constant is evaluated and discussed herein.