Synthesis, Electronic Structure, and Electron Transfer Dynamics of (Aryl)ethynyl-Bridged Donor−Acceptor Systems

Abstract

The ET dynamics of a series of donor-spacer-acceptor (D-Sp-A) systems featuring (porphinato)zinc(II), (aryl)ethynyl bridge, and arene diimide units were investigated by pump-probe transient absorption spectroscopy. Analysis of these data within the context of the Marcus-Levich-Jortner equation suggests that the pi-conjugated (aryl)ethynyl bridge plays an active role in the charge recombination (CR) reactions of these species by augmenting the extent of (porphinato)zinc(II) cation radical electronic delocalization; this increase in cation radical size decreases the reorganization energy associated with the CR reaction and thereby attenuates the extent to which the magnitudes of the CR rate constants are solvent dependent. The symmetries of porphyrin-localized HOMO and HOMO-1, the energy gap between these two orbitals, and D-A distance appear to play key roles in determining whether the (aryl)ethynyl bridge simply mediates electronic superexchange or functions as an integral component of the D and A units.

Long‐Lived, Emissive Excited States in Direct and Amide‐Linked Thienyl‐Substituted RuII Complexes

“…[16][17][18][19][20] Ruthenium based dyads and triads have been investigated with both saturated and π-conjugated linkers between the core and the peripheral substituents, in an effort to mediate electron transfer. [4,[21][22][23] As expected, it has been shown that both the length and the nature of the linker greatly influence the properties of molecular wire-like electron and energy transfer behavior within these assemblies. [4,14,[24][25][26][27] Previously, we have reported homoleptic Ru II dyads that exhibit long charge-separated state lifetimes resulting from the formation of an excited state comprised of three equilibrating states.…”

Controlling electron exchange in molecular assemblies

“…(4)) [36]. Here, a slow rate of electron transfer is associated with a large energy gap and hence relatively weak electronic coupling.…”

Specular neutron reflectivity and the structure of artificial protein maquettes vectorially oriented at interfaces

“…Thus the designed molecular functionality can be translated into a macroscopic material property. For example, previously designed four-helix bundle motifs [1], with apposed histidine residues at selected positions within the bundle for the bishistidyl coordination of metallo-porphyrin based prosthetic groups, can be used to generate interesting electron transfer [2][3][4] and nonlinear optical properties [5,6] at the molecular level. These can be vectorially oriented at a macroscopic interface also through their design [7].…”