Fused Pyrene–Diporphyrins: Shifting Near‐Infrared Absorption to 1.5 μm and Beyond

Abstract

Porphyrins have been explored for a number of potential optoelectronic applications that require strong absorption in the near-infrared (NIR) spectral region; these applications include organic electronics, [1,2] nonlinear optics, [3] and telecommunication technologies. [4] Porphyrins have also been investigated as active materials in photovoltaic cells [1] because of their high efficiency of charge separation and transport, [5] strong absorbance in the visible region, high chemical stability, and the ease with which their optoelectronic properties can be tuned with chemical modification. [6] The absorption bands of porphyrins are not readily shifted into the deepred and NIR spectral regions, and also tend to be narrow, thus minimizing their overlap with the solar spectrum. Triply bridged, (b, meso, b), porphyrin tapes (Figure 1 a, n = 0-22) show marked red-shifts in the porphyrin absorption bands, which extend deep into the NIR region. [7, 8a] Triply fused porphyrins with n = 1,2 give absorbance in the mid-NIR region (i.e., conventional wavelengths for telecommunications, ca. 1.5 mm), however, these porphyrins are difficult to synthesize, have low solubility, and are isolated only in small quantities. [8] Triply connected porphyrin dimers (Figure 1 a, n = 0) have a strong absorbance at l = 1050 nm, are photoand chemically stable, have a high solubility, and can be easily prepared from monoporphyrins. [7] Development of new organic dyes based on these accessible porphyrin dimers with absorption at the wavelengths for telecommunications (l = 1.5 mm) still remains a challenge.Extending the size of p conjugation in porphyrin systems results in most cases in a bathochromic (red) shift of the absorption. [7, 8b,c] The conjugation of porphyrin dimers can be extended through several modes of substitution involving the meso, (b, b), (b, meso) and (b, meso, b) positions. For diporphyrins substituted with two alkyne groups at the terminal meso positions, the Q band is red-shifted by 130 nm (l = 1181 nm) relative to the parent dimer. [9] In contrast, extending the conjugation in porphyrin dimers by benzannulating b,bpyrrolic positions red-shifts the Q band by only 18 nm, and the resulting compounds have poor solubility. [8b] Recently, it has been shown that anthracene rings can be fused to porphyrin dimers through the (b, meso, b) mode, which leads to a red-shift of the Q band to 1495 nm. [8c] However, the anthracene-fused diporphyrin exhibits the same undesirable difficulties found with higher porphyrin tapes, for example, synthetic difficulty, low yields and low solubility. [8c] Moreover, fusion of anthracene rings is limited only to alkoxy-substituted derivatives.The effects of aromatic ring fusion to porphyrin tapes in a (meso, b) mode have not been explored. We have analyzed the structures of the diporphyin core (Figure 1 b), a (b, meso, b) triply fused aromatic system (Figure 1 c), and a (b, meso) doubly fused molecule (Figure 1 d) using standard DFT methods. Significant bathochromic shifts of the lowestenerg...

Efficient Complexation of Pyrrole‐Bridged Dizinc(II) Bisporphyrin with Fluorescent Probe Pyrene: Synthesis, Structure, and Photoinduced Singlet–Singlet Energy Transfer

“…X-ray structures of both dizinc(II) bisporphyrin host and pyrene-encapsulated complex are also reported here, which gives a rare opportunity to investigate the structural and conformational change upon substrate binding. Although pyrene-porphyrin interactions have already been reported in the literature, [13] to the best of our knowledge the encapsulated pyrene complex reported here is the first structurally characterized host-guest assembly in which the p-electron-rich guest pyrene has been bound strongly enough to remain intact within the bisporphyrin cleft in both solid and solution. The stability of the host-guest complex also allows for its isolation as an analytically pure solid in good yields.…”

Triply Linked Porphyrinoids

“…As an extended derivative, anthracene‐fused porphyrin tape 11 was synthesized, which exhibits a NIR band at 1495 nm. Pyrene‐fused porphyrin tape 12M were also prepared . In this case, oxidative fusion reaction with DDQ‐Sc(OTf) 3 only furnished triply linked porphyrin dimer and following Scholl reaction with FeCl 3 eventually gave a pyrene‐fused porphyrin tape 12Zn .…”

Indachlorins: Nonplanar Indanone‐Annulated Chlorin Analogues with Panchromatic Absorption Spectra between 300 and 900 nm

“…These derivatives exhibit intense and broad optical spectra that span, with no entirely transparent regions, an impressive range from the UV to the NIR region. Although porphyrinoids with longer λ max values,10a–c, e, 11, 15 “blackened” porphyrins with absorption in the range between 300 and 725 nm,13 or di‐ and oligomeric porphyrins with near‐panchromatic properties, were presented previously,2 the combination of the following features make the indachlorins unique:…”