Novel aza-BODIPY derivatives substituted with heavy atoms such as bromine and iodine were synthesized, and their triplet and singlet oxygen generation efficiencies have been investigated. These derivatives showed absorption in the NIR region with high molar extinction coefficients. The dye substituted with four iodine atoms showed yields of Φ(T) = 0.78 and Φ((1)O(2)) = 0.70, which are the highest values so far obtained for the aza-BODIPY derivatives.

The design and development of novel squaraine dyes as sensitisers for photodynamic therapy (PDT) applications has grown tremendously in the last decade from the time when a squaraine dye was proposed to be a potential candidate, to-date when the use of such dyes have been demonstrated in animal models for skin cancer. This perspective article highlights the basic design, tuning of absorption, triplet excited state and two-photon absorption properties and recent developments of the squaraines as PDT sensitisers.

A new series of aza-BODIPY derivatives (4 a-4 c, 5 a,c, and 6 b,c) were synthesized and their excited-state properties, such as their triplet excited state and the yield of singlet-oxygen generation, were tuned by substituting with heavy atoms, such as bromine and iodine. The effect of substitution has been studied in detail by varying the position of halogenation. The core-substituted dyes showed high yields of the triplet excited state and high efficiencies of singlet-oxygen generation when compared to the peripheral-substituted systems. The dye 6 c, which was substituted with six iodine atoms on the core and peripheral phenyl ring, showed the highest quantum yields of the triplet excited state (Φ(T) =0.86) and of the efficiency of singlet-oxygen generation (Φ(Δ) =0.80). Interestingly, these dyes were highly efficient as photooxygenation catalysts under artificial light, as well as under normal sunlight conditions. The uniqueness of these aza-BODIPY systems is that they are stable under irradiation conditions, possess strong red-light absorption (620-680 nm), exhibit high yields of singlet-oxygen generation, and act as efficient and sustainable catalysts for photooxygenation reactions.

Cyclophanes possess a defined cavity size and are efficient in encapsulating and stabilising guest molecules inside the cavity through various non-covalent interactions. This unique property of the cyclophanes has been widely exploited for the development of selective probes for a variety of guest molecules. The present tutorial review highlights the use of various interesting functionalised cyclophane architectures for the sensitive and selective optical recognition of important biomolecules.

pKa-matched monomers self-assemble into supramolecular polymers at pH 7, producing hydrogels with high pH sensitivity.