Red Aqueous Room-Temperature Phosphorescence Of Naphthalene Diimide Derivative Modulated By Anion-π And Cucurbit[n]uril-based Host-Guest Interactions

Purely organic room temperature phosphorescent（ORTP）materials have been potential in applications including light-emitting diode（LED）,analysis,information store,anti-counterfeiting technology and bioimaging,due to advantages of cheapness,easy preparation and low biotoxicity.It is intriguing but also challenging to explore aqueous ORTP materials for bio-analysis and bio-imaging technologies.Since 2010,numerous researches have unravelled the great significance of inter-and intramolecular non-covalent interactions in efficient solid ORTP and provided theoretical bases for researches on aqueous ORTP materials.However,due to the severe hydration and quenching effects by water,it is still challenging to realize efficient aqueous ORTP by enhancement of inter-and intramolecular non-covalent interactions between phosphors in water.By steady&gated emission spectroscopy,¹H NMR,ESI-MS,DLS and DFT simulation,this thesis focuses on the effects of non-covalent interactions（anion-πand intermolecular stacking interaction）of a water-soluble naphthalene diimide derivative（2Br-NDI）and its host-guest recognition with CB[n]s（n=7,8,10）on the aqueous ORTP properties of 2Br-NDI.It was revealed that the aqueous ORTP of 2Br-NDI was determined by its supramolecular states in water:both the intensity and lifetime of aqueous ORTP of 2Br-NDI were decreased at high concentration（>125?M）due to the intermolecular stacking of 2Br-NDI along its short axis;at concentration<125?M,it was experimentally proved that the anion-πinteraction between Cl^-and 2Br-NDI in water could be synergistically stabilized by H-bonding interaction and electrostatic attraction.Interestingly,the anion-πinteraction could induce an aqueous thermally-activated delayed singlet charge transfer fluorescence(¹CT_delay)distinct to the intrinsic triplet emission（T₁）of 2Br-NDI.Further supramolecular recognition between 2Br-NDI and CB[n]s weakened the anion-πinteraction between Cl^-and 2Br-NDI in water and modulated the aqueous ORTP emission of 2Br-NDI.Specifically,dumbbell-shaped 2:1 host-guest complex was formed between CB[7]and 2Br-NDI with less enhancement of ORTP of 2Br-NDI due to the exposure of 2Br-NDI core.1:2 inclusion complex was formed between CB[10]and 2Br-NDI with the enhanced aqueous ORTP efficiency and attractive resistance against oxygen quenching.Distinct to（CB[7]）₂·（2Br-NDI）,CB[10]·（2Br-NDI）₂ and the other reported CB[n]-based inclusion complexes for aqueous ORTP,2Br-NDI formed1:1 exclusion complex with CB[8]and exhibited the strongest and longest-lived ORTP in water among all cases researched.It was revealed that the non-covalent nπ^*-ππ^*electronic coupling interaction in water between the electron-rich carbonyl rims of CB[8]and the electron-deficient 2Br-NDI core could be enhanced by their host-guest recognition via cation-dipole interaction,dramatically promoting the ISC process and finally resulting in the intriguing aqueous ORTP properties.Both the anion-πinteraction in water between naphthalene diimide（NDI）derivatives and halogen anion and the intermolecular nπ^*-ππ^*electronic coupling for aqueous ORTP enhancement have been rarely reported and challenging.NDI-based anion-πinteraction could be realized in organic solvents while intermolecular nπ^*-ππ^*electronic coupling for ORTP enhancement only in solid,yet.In this thesis,we experimentally evidenced that the anion-πinteraction in water between 2Br-NDI and Cl^-could be synergistically stabilized by H-bonding and electrostatic attraction interactions,inducing a characteristic aqueous ¹CT_delay emission with a higher energy level than T₁ of2Br-NDI.The synergistic strategy provides theoretical base for designing more materials for anion recognition in water.On the other hand,intermolecular nπ^*-ππ^*electronic coupling for aqueous ORTP enhancement was realized by the cation-dipole interaction between 2Br-NDI and CB[8],which might inspire the exploration of more aqueous ORTP materials for bio-analysis and bio-imaging.Meanwhile,the cavity-free CB[8]and the externally-bound 2Br-NDI were believed to be attractive characteristics for designing novel stimuli-responsive functional materials in the future.