Abstract
Connecting two porphyrin units in a rigid linear fashion, without any undesired electron delocalization or communication between the chromophores, remains a synthetic challenge. Herein, a broad library of functionally diverse multi‐porphyrin arrays that incorporate the non‐traditional rigid linker groups cubane and bicyclo[1.1.1]pentane (BCP) is described. A robust, reliable, and versatile synthetic procedure was employed to access porphyrin‐cubane/BCP‐porphyrin arrays, representing the largest non‐polymeric structures available for cubane/BCP derivatives. These reactions demonstrate considerable substrate scope, from utilization of small phenyl moieties to large porphyrin rings, with varying lengths and different angles. To control conformational flexibility, amide bonds were introduced between the bridgehead carbon of BCP/cubane and the porphyrin rings. Through varying the orientation of the substituents around the amide bond of cubane/BCP, different intermolecular interactions were identified through single crystal X‐ray analysis. These studies revealed non‐covalent interactions that are the first‐of‐their‐kind including a unique iodine‐oxygen interaction between cubane units. These supramolecular architectures indicate the possibility to mimic a protein structure due to the sp3 rigid scaffolds (BCP or cubane) that exhibit the essential conformational space for protein function while simultaneously providing amide bonds for molecular recognition.
Highlights
Defined molecular architectures are a prerequisite for the logical construction of multifunctional chemical systems
The 3D, compact, electronically isolating, and saturated structures of cubane and BCP enable them to avoid undesirable p–p stacking which may lead to improved solubility of chromophoric arrays
Amide bonds have been introduced at the bridgehead carbons of cubane and BCP,[13] most of these reported moieties were used as bioisosteres[8] or in crystal engineering.[9]
Summary
A straightforward strategy for avoiding any undesirable overlap of the p-systems may be to attach two porphyrin skeletons through non-traditional rigid scaffolds such as bicyclo[1.1.1]pentane (BCP) or cubane These saturated entities are transparent to UV/Vis light and exhibit specific three-dimen-. The 3D, compact, electronically isolating, and saturated structures of cubane and BCP enable them to avoid undesirable p–p stacking which may lead to improved solubility of chromophoric arrays Despite their desirable well-defined dimensions and rigid-rod geometries, the chemistry of these moieties is undeveloped, in terms of functionalization or CÀH-activation at the bridgehead carbons.[7]. Amide bonds have been introduced at the bridgehead carbons of cubane and BCP,[13] most of these reported moieties were used as bioisosteres[8] or in crystal engineering.[9] These compounds have the potential to be utilized as molecular building blocks. We present porphyrin units bridged through non-traditional BCP/cubane connectors as a test case for multichromophoric and/or electroactive systems in general
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