Attachment of different donor groups to a cryptand for modulation of two-photon absorption cross-section

Two-photon absorption (TPA) properties of a laterally nonsymmetric aza cryptand with attached side arms have been investigated. This series of Schiff base derivatives supports the mechanistic approach for enhancing the TPA process, which is usually dictated by molecular geometry, π-bridging, derealization length, and corresponding charge-transfer possibilities. The results described here suggest that on increasing the branching units, the TPA cross-section, σ⁽²⁾, can be tuned to a larger value. The TPA activity is synthetic strategy for designing novel octupolar molecules with high σ⁽²⁾ values. Theoretical calculations at the B3LYP functional with the 6-31G* basis set under DFT formalism provide supporting evidence that the communication between the side arms through the metal d orbital and more ordered geometry of chromophores leads to a smaller HOMO-LUMO gap, which has a great influence upon the electronic properties of the molecules. "switched on" when a metal atom enters the cavity and serves as a conduit of electronic derealization. The σ⁽²⁾ value increases as the donor strength increases. The maximum value is obtained on moving from the singlebranched system to the nearly three-fold symmetry. This serves as a useful