Porphyrinoids chirality

Keywords Supramolecular chemistry Chirality Porphyrinoids Host-guest Aggregation... 

The third type of review primarily focused on the different aspects of chirality and contained some porphyrin-based supramolecular chirogenic systems as examples. For example, Finn, Wenzel, and Wilcox discussed various methods and reagents for the determination of ee and absolute configuration using different spectroscopic approaches [35,36] whilst Allenmark, Pasternack, Kobayashi, Formaggio et al. addressed the induced and electronic CD upon the intra- and intermolecular interactions considering several porphyrinoid chromophores [37-40]. 

The representative examples of chirogenic assemblies on the basis of achiral monomeric porphyrinoids exposed to a chiral influence clearly show their great importance and wide applicability in various fields. The major chiroptical properties of these relatively simple supramolecular systems include transferring the chiral information and controlling the induced asymmetry by different factors. However, another type of chirogenic process— modulation of inherent chirality is going to be illustrated for chiral porphyrins in the next sections. 

In contrast to achiral/racemic porphyrinoids, the chirogenic properties of chiral porphyrinoids have been scantily investigated despite their prime importance for chiral recognition, asymmetric catalysis, medical purposes, and various biomimetic studies. 

Chirogenic supramolecular systems based on dimeric/oligomeric porphyrinoids can also be classified according to their complexity and structural features. First, the assemblies consisting of two or more monomeric porphyrins fixed in an asymmetrical fashion by chiral bridges via supramolecular binding will be examined. 

Supramolecular systems on the basis of dimeric and oligomeric porphyrinoids are varied depending upon the chirality of the supramolecular counterparts, type of the covalent linkage, and number of the porphyrin subunits. Firstly, we shall examine examples of the assemblies consisting of achiral and racemic bis-porphyrinoid hosts and chiral guests. 

Fig-i Schematic representation of chirality sensing of enantiomeric guests by achiral bis-porphyrinoids... 

However, chiral recognition was the most common field of application of various chiral bis-porphyrinoids. Hence, Sessler s group prepared a series of bis-sapphyrins 67-69 for the chiral recognition of dicarboxylate anions via a combination of Coulombic attractions and hydrogen bonding [119]. While... 

The supramolecular assemblies involving aggregated porphyrinoids similarly to other types of previously discussed systems could be reasonably divided into different categories on the basis of achiral, chiral monomeric, and dimeric porphyrinoids. Again, the simplest monomeric achiral porphyrinoids will be presented first. 

Since this class of supramolecular assemblies is represented by a small number of examples due to the enhanced structural intricacy and synthetic complexity, we shall present both chiral and achiral dimeric/oligomeric porphyrinoid-based systems in one section. 

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