Extremely Non-Planar Phthalocyanines with Saddle or Helical Conformation:  Synthesis and Structural Characterizations

Abstract

Most of the applications of phthalocyanines (Pcs) are concerned with the large, flat π-conjugation system, as well as the type of central metal. 1 In particular, it is well-known that, compared with porphyrins, 2 the metalloPcs (MtPcs) have extremely high planarity: for example, nonsubstituted NiPc is essentially perfectly planar, 3 although MtPcs with larger metal ions such as Pb and Sn distort the geometry to some extent. 4 Structurally distorted Pcs have been reported in the past few years, where the steric congestion of substituents caused distortion of the macrocycle. 4,5 In this communication, we report two types of Pc analogues whose nonplanarity appears to be the highest yet reported. To induce the largest distortion conceivable, aromatic ortho-dinitriles having two protruding phenyl groups, 3 and 4, are used. These types of dinitriles have long been believed to be too congested to form Pcs by themselves 6 and have therefore been employed for the preparation of opposite type of MtPc analogues, utilyzing the steric hindrance between the phenyl groups. 7 In the course of studies, however, we thought that, if these dinitriles can occupy the adjacent positions of Pcs, the deviation from planarity would be very large because of the overlap of the protruding phenyl groups. 8 As described below, we have overcome this problem, and the resultant two Pc analogues obtained by the above inverse concept, 1 and 2, are indeed confirmed to be the most nonplanar Pcs ever substantiated structurally.Both 1 9 and 2 10 were prepared by the so-called lithium method 1 at ca. 170 and 150 °C, respectively (Scheme 1). In the case of 2, dinitriles 4 and 5 were co-macrocyclized, so that repeated chromatography was inevitably required. They were characterized using mass spectra, elemental analysis, and 1 H NMR (only for 1) 9,10 and their molecular structures were analyzed by X-ray crystallography. Crystals were grown in either chloroform-hexane (1) or acetone-containing toluene (2).

Optical and Electrochemical Properties of Non-Peripheral Thioaryl-Substituted Subphthalocyanine as Precursors for Dye-Sensitizer to Develop Photovoltaic Cells

“…The compounds 3 have distorted molecular structure. Similar phenomena were observed bulky substituted phthalocyanines [5] [21] [22]. In order to make unsymmetric 3:1 type phthalocyanines were reacted to obtain metal-free corresponding phthalocyanines.…”

“…Then, the electron distribution is changed in subphthalocyanine ring. The steric hindrance arises from substituted thioaryl groups, which appear to be as significant [22]. The authors think that the bathochromic effects of Q bands in compounds 3 arise from the steric hindrance of molecular structure similar to phthalocyanines having bulky substituents [5] [21] [22].…”

“…Then, the non-peripheral (1,4,8,11,15,18,22,25) substituted phthalocyanines can show a bathochromic effect in comparison with the peripheral position [4] [19].…”

“…Alkyl substituents linked through heteroatoms have the important effect of moving the Q band to the nearinfrared region [20]. Then, the Q band of nonplanar non-peripheral substituted octakis(p-methoxyphenyl)phthalocyanines was shifted beyond 800 nm [21] [22]. Although most metal phthalocyanines have a planar structure, the bathochromic effect of the Q band observed for the octakis(p-methoxyphenyl)phthalocyanines arises from ligand deformation [21] [22].…”

“…Then, the Q band of nonplanar non-peripheral substituted octakis(p-methoxyphenyl)phthalocyanines was shifted beyond 800 nm [21] [22]. Although most metal phthalocyanines have a planar structure, the bathochromic effect of the Q band observed for the octakis(p-methoxyphenyl)phthalocyanines arises from ligand deformation [21] [22]. Moreover, the authors have reported that the Q bands of non-peripheral substituted octakis(thioaryl)phthalocyanines appeared at around 860 nm [5].…”