3,6,13,16-Tetrasubstituted Porphycene: The Missing Link in Porphycene Chemistry

Abstract

We have introduced the first 3,6,13,16-tetrasubstituted porphycene as its tetramethoxy analogue. This substitution pattern is one of the most general patterns yet missing in this isomeric porphyrin chemistry. This porphycene exhibits intense fluorescence along with the ability to coordinate with divalent metal ions; in particular, it forms the first stable Zn­(II) complex among the tetrasubstituted porphycenes. Notably, the molecular structure of Zn1•Py displays supramolecular chirality.

3,6,13,16-Tetraalkylporphycenes: synthesis and exploration of the effect of alkyl groups on the structure, photophysical properties, and basicity

“…17b Although several types of peripheral substitutions have been explored, the synthesis of 3,6,13,16substituted porphycenes eluded chemists for more than three decades, 1b,c until our recent report of 3,6,13,16-tetramethoxyporphycene. 18 As expected it provided a square type core and formed complexes with various metal ions, including Zn(II) that showed supramolecular chirality in the solid state. However, we could achieve its synthesis through reductive dehalogenation of 2,7,12,17-tetrachloro-3,6,13,16-tetramethoxyporphycene or more preferably by subjecting the dechlorination reaction upon its precursor dichlorodimethoxybipyrrole dialdehyde 19a to obtain 3,3 0 -dimethoxybipyrrole dicarbaldehyde and performing McMurry coupling upon it.…”

“…17a However, Vogel found that the methyl substituents at the 2,7,12,17-positions impart greater structural deviations in the fused dibenzoporphycenes compared to the t-butyl groups. 22 Further, 1a displayed a square-type N4-core (N1-N2: 2.73 Å; N1-N4: 2.77 Å) like that found in the case of the tetramethoxy analogue 18 and the core was very similar to that of both etioporphycene and b-octaethylporphycene. 17a This clearly indicates that the outer b-substituents have minimal implications upon the structure of porphycenes, an attribute earlier reported upon exchange of methoxy with chloro groups at those positions.…”

“…However, we could achieve its synthesis through reductive dehalogenation of 2,7,12,17-tetrachloro-3,6,13,16-tetramethoxyporphycene or more preferably by subjecting the dechlorination reaction upon its precursor dichlorodimethoxybipyrrole dialdehyde 19a to obtain 3,3 0 -dimethoxybipyrrole dicarbaldehyde and performing McMurry coupling upon it. 18 This route is found to possess limited utility as a general synthetic route because the starting material 3-chloro-4-methoxypyrrole-2-carbaldehyde for dichlorodimethoxybipyrrole dialdehyde could only be obtained during exhaustive Vilsmeier-Haack formylation of 3,4-dimethoxypyrrole. 19b Very recently, we synthesized 3,6,13,16-tetrapropylporphycene 1c following a rational approach after exploring several synthetic routes towards the precursor 3,3 0 -dipropylbipyrrole dicarbaldehyde.…”

In-Core N4-Coordination of Palladium(II) in Dinaphthoporphycene: Synthesis, Structure, and Photophysical Studies

“…This was clearly evident in type A and type B porphycenes having substituents at the meso - and outer-β-pyrrolic positions, respectively (Figure ), where coordination with metal ions was found to be difficult to perform. ,, Vogel found the presence of substituents at the 3,6,13,16-positions in β-octaalkylporphycenes reduced the strength of the NH···N hydrogen bond owing to nonbonding interactions, thereby making the macrocyclic core more of a square-type . After more than three decades, we recently synthesized the first 3,6,13,16-substituted porphycene (type C ), which was found to display slightly stronger NH···N hydrogen bonding than the type D analogues . Further, they are endowed with the best attributes of porphycenes in terms of their coordination chemistry and photophysical properties.…”

“…13c After more than three decades, we recently synthesized the first 3,6,13,16-substituted porphycene (type C), which was found to display slightly stronger NH•••N hydrogen bonding than the type D analogues. 15 Further, they are endowed with the best attributes of porphycenes in terms of their coordination chemistry and photophysical properties.…”