Self-assembled nanorods of bay functionalized perylenediimide: Cu2+ based ‘turn-on’ response for INH, complementary NOR/OR and TRANSFER logic functions and fluorosolvatochromism

Abstract

We designed and synthesized the mono bay functionalized perylenediimide (PDI) derivative PDI-DMEA which undergoes self-assembly to form a nanorod morphology. The diameter of these nanorods is in the range of 150–300 nm and the length extended up to the μm range. These nanorods on interaction with Cu²⁺ ions transformed into spherical aggregates having a diameter of 350–600 nm in accordance with DLS studies. In solution, PDI-DMEA shows a blue shift of the internal charge transfer (ICT) absorption band from 605 to 570 nm along with a hyperchromic effect at 570 nm, in the presence of 0.7 equivalents of Cu²⁺ ions. The addition of 2 equivalents of Cu²⁺ ions results in complete disappearance of the ICT band at 570 nm and appearance of a normal absorption band of PDI at 515 nm (a visual colour change from colourless to yellow). On the other hand PDI-DMEA shows a strong fluorescence ‘turn-on’ response at 537 and 573 nm on addition of higher equivalents of Cu²⁺ ions. Thus, PDI-DMEA represents several examples of molecular switches such as ‘OFF–ON–OFF’ and ‘ON–OFF–ON’ at 570/515 nm (Cu²⁺, absorbance), and ‘OFF–ON’ at 570 nm (Fe²⁺, absorbance) and 537 nm (Cu²⁺, fluorescence) and thus offers the possibility for developing NOR, OR, INH and TRANSFER logic and complimentary logic circuits. Moreover, PDI-DMEA and the PDI-DMEA–Cu²⁺ complex show fluorosolvatochromism which helps to develop a colour array for differentiating organic solvents. The detailed mechanism of interaction of Cu²⁺ and Fe²⁺ with PDI-DMEA, confocal laser scanning microscopic studies, dynamic light scattering, ¹H NMR titration and reversibility are discussed.