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 lowestenergy transiti...

Triply Linked Porphyrinoids

“…Pyrene-fused porphyrin tape 12M were also prepared. [27] 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 ap yrene-fused porphyrin tape 12Zn.A cidic demetalation afforded freebase 12 H, to which Pb(OAc) 2 wasa dded to give the corresponding metal complex 12Pb.I nterestingly, 12Pb shows the most red-shifted absorption bands at 1459 nm as compared with those of 12H (1269 nm) and 12Zn (1323 nm) in line with the opticalp roperties of the porphyrin metal complexes. [28] Unusual cycloaddition reactions occurreda tt he bay-area of porphyrin tape (Scheme 2).…”

The Synthesis and Coating of Long, Thin Copper Nanowires to Make Flexible, Transparent Conducting Films on Plastic Substrates

“…Besides being useful for applications in communications, the greater transmittance of CuNW fi lms in the infrared could be used to improve the effi ciency of infrared photovoltaics. [ 10 ] A major advantage of fi lms of metal nanowires is that they are much more fl exible than brittle fi lms of ITO. To demonstrate the fl exibility of the CuNW fi lms, fi lms with a specular transmittance of 85% were subjected to both compression and tension bending from a radius of curvature of 10 mm to a radius of curvature of 2.5 mm (Figure 3 E inset).…”

Near‐Infrared (>1000 nm) Light‐Harvesters: Design, Synthesis and Applications

“…Upon transmetalation of Ph-17 with Pb II the new molecule (Ph-19) shows am ore broad and red shifted Qb and (l max = 1459 nm). [36] Nearly all phthalocyanines (Pcs) have their principal absorption band (Q band) at 650-700 nm. However the Q-band can be shifted towards NIR region by benzoannulation to make naphthalocyanine (Nc) and further anthracocyanine (Ac), the drawback of this process is that it destabilizes the HOMO energy level, and hence makes the resulting Ncs and Acs air sensitive.…”