Herein, we revealed a symmetry-breaking charge transfer (SBCT) process in the excited state of a directly linked push-pull porphyrin dyad (AD) and triad (ADA) via spectroscopic measurements including steady-state absorption and fluorescence, time-resolved fluorescence (TRF), femtosecond transient absorption (fs-TA), and time-resolved infrared (TRIR) measurements. Unprecedented broad fluorescence spectra were observed for porphyrin arrays in polar solvents; these were attributed to the existence of a charge transfer state as evidenced by the TRF measurements. TA measurements also revealed emerging features of a CT state for AD and ADA in polar solvents. These dynamics were also confirmed via TRIR measurements, which provided further information on the solvation and structural relaxation processes of the SBCT process. This is the first observation of an SBCT process in porphyrin arrays, providing fundamental understanding of the strongly coupled porphyrin arrays. Thus, the results of this study reveal the potential of the porphyrin arrays in relevant applications requiring SBCT.

The scientific significance of excited-state aromaticity concerns with the elucidation of processes and properties in the excited states. Here, we focus on TMTQ, an oligomer composed of a central 1,6-methano[10]annulene and 5-dicyanomethyl-thiophene peripheries (acceptor-donor-acceptor system), and investigate a two-electron transfer process dominantly stabilized by an aromatization in the low-energy lying excited state. Our spectroscopic measurements quantitatively observe the shift of two π-electrons between donor and acceptors. It is revealed that this two-electron transfer process accompanies the excited-state aromatization, producing a Baird aromatic 8π core annulene in TMTQ. Biradical character on each terminal dicyanomethylene group of TMTQ allows a pseudo triplet-like configuration on the 8π core annulene with multiexcitonic nature, which stabilizes the energetically unfavorable two-charge separated state by the formation of Baird aromatic core annulene. This finding provides a comprehensive understanding of the role of excited-state aromaticity and insight to designing functional photoactive materials.

The photodissociation dynamics of CF 2 ICF 2 I in solution was investigated from 0.3 ps to 100 μs, after the excitation of CF 2 ICF 2 I with a femtosecond UV pulse. Upon excitation, one I atom is eliminated within 0.3 ps, producing a haloethyl radical having a classical structure: anti-CF 2 ICF 2 and gauche-CF 2 ICF 2 . All the nascent gauche-CF 2 ICF 2 radicals reacted with the dissociated I atom within the solvent cage to produce a complex, I 2 ••C 2 F 4 , in <1 ps. The quasi-stable I 2 •• C 2 F 4 complex in CCl 4 (CH 3 CN or CD 3 OH) further dissociated into I 2 and C 2 F 4 with a time constant of 180 ± 5 (46 ± 3) ps. Some of the anti-CF 2 ICF 2 radicals also formed the I 2 ••C 2 F 4 complex with a time constant of 1.5 ± 0.3 ps, while the remaining radicals underwent secondary elimination of I atom in a few nanoseconds. The time constant for the secondary dissociation of I atom from the anti-CF 2 ICF 2 radical was independent of the excitation wavelength, indicating that the excess energy in the nascent radical is relaxed and that the secondary dissociation proceeds thermally. The formation of the I 2 ••C 2 F 4 complex and the thermal dissociation of the anti-CF 2 ICF 2 radical clearly demonstrate that even a weakly interacting solvent plays a significant role in the modification and creation of reaction.

Photoexcited CF2I2in c-C6H12undergoes various secondary reactions including complex and isomer formation, after ultrafast two- or three-body dissociations.

NO photorelease and its dynamics of two {RuNO}6 complexes, Ru(salophen)(NO)Cl (1) and Ru(naphophen)(NO)Cl (2), with salen-type ligands bearing π-extended systems (salophenH2 = N,N'-(1,2-phenylene)-bis(salicylideneimine) and naphophenH2 = N,N'-1,2-phenylene-bis(2-hydroxy-1-naphthylmethyleneimine)) were investigated. NO...