Synthesis And Properties Of Multi-stimulated Response Fluorescent Molecules Based On Rhodamine

Stimulus-responsive fluorescent materials can dynamically and reversibly convert fluorescence intensity and color under stimulation of external environment,such as mechanical force,heat,light,acid and alkali,electromagnetic,etc.,which are widely used in optoelectronic devices,information storage,and chemistry sensing,fluorescent probes,bio-imaging and so on.Since most fluorescent chromophores have an aggregation-induced quenching(ACQ)phenomenon in the solid state,the stimuli response ability is lowered,and fluorescence changes are not obvious,which greatly limits application of stimuli-responsive materials.Therefore,designing and synthesizing novel solid-state stimuli-responsive fluorescent materials and exploring their molecular design rules are very important.The C-N weak bond in Rhodamine can be broken under external stimulation,then ring-opening reaction occurs,with absorption and emission change during structural isomerization from the spirolactam ring.In our work,Rhodamine are used as mother nucleus.After modification with fluorescent chromophores,such as naphthalimide and spiropyran,a series of excellent stimuli-responsive materials in solid state are designed and synthesized.And we achieved high-contrast,highly-sensitive and reversible stimuli-responsive materials.System 1:we designed and synthesized a novel molecule 2NR with two 1,2-naphthalimide moieties and a rhodamine 6G unit linked by a branched amidoamine spacer.2NR exhibits excellent acid and force dual-stimuli-responsive behaviour in the solid state.The branched amidoamine spacer induces a twisted conformation of naphthalene moieties,which provides considerable free volume and significantly facilitates the isomerization process of R6G from spirolactam to open-ring amide,so that rhodamine has excellent stimulating response behavior in the solid state.System 2:we designed and synthesized a molecule Rh-SP with dipeptide as a spacer to link rhodamine B and spiropyran moieties.Rh-SP exhibits efficient photochromic properties both in solution and solid state.High-contrast fluorescence switch is also realized under the stimulus of external force.Since both rhodamine and spiropyran have weak bonds,it is easy to break successively under mechanical force.The material has potential application value in the fields of anti-counterfeiting materials and information storage.