Synthetic, Structural, and Spectroscopic Studies of Bis(porphyrinzinc) Complexes Linked by Two‐Atom Conjugating Bridges

Abstract

Four ZnII 5,10,15‐triphenylporphyrin (TriPP) complexes meso–meso linked by two‐atom bridges, namely, C2H2 (2), C2 (3), CH=N (4), and N2 (5), were prepared, for comparison of ground‐state inter‐porphyrin conjugation. The X‐ray crystal structure of azoporphyrin 5·py2 (py = pyridine) was determined: it exhibits a stepped‐offset shape and a porphyrin–azo torsion angle of 34.8°. Some new monoporphyrin starting materials were prepared, and ZnTriPPNH2 (27), ZnTriPPCHO (23), NiTriPPCHO (7), and ZnTriPPCH2CH2Ph (18), as well as the byproduct butadiyne‐linked dimer 26 were characterized by single‐crystal X‐ray crystallography. The conjugation in the dimers was assessed by electronic absorption and steady‐state fluorescence spectroscopy. All show variously split B bands: azoporphyrin 5 clearly has the strongest ground‐state inter‐porphyrin interactions. Imine 4 and azo 5 show strongly quenched fluorescence emission, which indicates the presence of efficient relaxation pathways afforded by the N‐containing linkers.

Ground State versus Excited State: Discrepancy in Electronic Communication in a Series of meso–meso Two‐Atom‐Bridged Diporphyrins

“…As previously reported, upon excitation at 420 or 480 nm 1 shows ab road and structurelessf luorescence with two maximaa t7 83 and 917 nm, which originate from the intermediate and planar conformers, respectively. [4,6] This was deduced from the corresponding excitation spectra (Figure S1 a in the Supporting Information), which resemble the full ground-state absorption spectrum. Additionally,u pon excitation into the highere nergy Soret-band absorption, aw eak fluorescencep eak is visible in the range of 600-650 nm (Figure 3b), which is absent upon 480 nm excitation.…”

“…[4,14] Data for 1: (bs, 4H). The syntheses of 1-3 were previously reported and compounds were verified by 1 HNMR spectroscopy.…”

“…The syntheses of 1-3 were previously reported and compounds were verified by 1 HNMR spectroscopy. [4,14] Data for 1: 76 (m, 18 H), À1.38 ppm (bs, 4H). [4,14] Electrochemistry Cyclic voltammetry and differential pulse voltammetry were performed at room temperature, under an argon atmosphere, and the applied potential was controlled with mAutolab III/FRA2 potentiostat from METROHM.…”

“…[4] These compounds uniquely contain doublyb ondedt wo-atom bridges,n amely trans-1,2-ethenediyl (1,e thene), 1,2-iminomethinediyl (2,i mine), and trans-1,2-diazenediyl (3,a zo) (Scheme 1), which has allowedc omprehensive comparative research on the photophysicso ft his class of diporphyrins to be conducted. [4] These compounds uniquely contain doublyb ondedt wo-atom bridges,n amely trans-1,2-ethenediyl (1,e thene), 1,2-iminomethinediyl (2,i mine), and trans-1,2-diazenediyl (3,a zo) (Scheme 1), which has allowedc omprehensive comparative research on the photophysicso ft his class of diporphyrins to be conducted.…”

Ullmann-like reactions for the synthesis of complex two-dimensional materials

“…Conjugated networks of porphyrins show potential for applications that require special light-absorbing and energy-transfer properties [8][9][10]. Developing and analyzing these materials and chemical processes can be a non-trivial process due to their low-dimensionality and high complexity.…”