One of the challenges for achieving efficient exciton transport in solar energy conversion systems is precise structural control of the light-harvesting building blocks. Here, we create a tunable material consisting of a connected chromophore network on an ordered biological virus template. Using genetic engineering, we establish a link between the inter-chromophoric distances and emerging transport properties. The combination of spectroscopy measurements and dynamic modelling enables us to elucidate quantum coherent and classical incoherent energy transport at room temperature. Through genetic modifications, we obtain a significant enhancement of exciton diffusion length of about 68% in an intermediate quantum-classical regime.

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We report a combined approach of stationary and timeresolved fluorescence measurements and ultraviolet−visible (UV−vis) transient absorption spectroscopy (TAS) along with ab initio calculations, which provide an overall picture of the dynamics occurring after excitation in a push−pull molecule, namely, 4,7-bis (4,5-dibutylbenzo-[1,2-b:4,3-b′]bisthiophene [1,2-b:4,3-b′]bisthiophen-2-yl)-2,1,3-benzothiadiazole. The analysis of the emission spectra in solvents of different polarities reveals the presence of three conformers whose structures differ in the orientation of the 4,5-dibutylbenzo-bisthiophene groups and in their planarity with respect to the benzothiadiazole acceptor group. The Kawski method allows us to estimate the ground-and first-excited state dipole moments (μ g and μ e ) for the three conformers. We find values of μ e similar for the three conformers and higher than the relative μ g values as can be expected from a push−pull molecule undergoing a light-induced charge-transfer (CT) transition. UV−vis TAS in different solvents highlights the instantaneous (within our instrumental resolution) formation of a locally excited S 1 state (accompanied by a big change in the dipole moment with respect to S 0 ), which undergoes a rapid intramolecular CT (ICT) assisted by molecule planarization [planar ICT (PICT)]. The strong dipole−dipole interactions with the polarized solvent molecules stabilize the S 1 CT state that decays principally through fluorescence emission. Both PICT and solvation dynamics are responsible for the big Stokes' shift characterizing the molecule, particularly in polar solvents. The fluorescence lifetimes are substantially longer in polar solvents, and also fluorescence quantum yields are higher in polar solvents. We conclude that the radiative relaxation time increases when molecular planarization of the S 1 emissive state takes place, and this condition is favored in polar solvents where local dipole−dipole interactions support the structural stabilization of the CT emissive state. In the poly(methyl methacrylate) matrix, the structural and solvation dynamics are strongly inhibited, leading to reduction of nonradiative processes and to shortening of the fluorescence relaxation time.

SUMMARY: A new class of highly effective homogeneous palladium bis(methoxycarbonyl) complexes Pd(L1L)(COOMe) 2 , where (L1L) are substituted phenanthroline ligands, has been developed for the production of syndiotactic alternating styrene-carbon monoxide copolymers. The essential feature of this novel catalytic system is that it is formed by palladium complex, Pd(L1L)(COOMe) 2 , an acid cocatalyst, (L1L)HPF 6 , bearing a weakly coordinating counter anion, and an oxidant, such as 1,4-naphthoquinone (1,4-NQ). The palladium/acid cocatalyst molar ratio has been explored. A maximum of copolymerization activity was obtained at 1/1 molar ratio. For a series of palladium catalysts, Pd(phen)(COOMe) 2 appeared to be the most active one. The effect of substituents at the ligand in Pd(L1L)(COOMe) 2 on the copolymerization activity was studied. The tacticity of alternating copolymers obtained with different Pd(L1L)(COOMe) 2 catalysts was determined by NMR spectroscopy. The copolymers were thermally characterised by TGA and DSC.