Fluorescent dye, preparation method therefor and use thereof

1. A fluorescent dye of formula (I):

wherein X and Y are independently selected from O, S, C(CH 3 ) 2 and NR 6 ;

R 1 is (CH 2 ) n−1 CH 3 , (CH 2 ) n R 7 , (CH 2 ) m C 6 H 5 or (CH 2 ) m C 6 H 4 R 7 ;

R 2 and R 3 are independently selected from H, F, Cl, Br, I, (CH 2 ) n−1 CH 3 , (CH 2 ) n R 8 , CH 2 C 6 H 5 , CH 2 C 6 H 4 R 8 , O(CH 2 ) n−1 CH 3 , O(CH 2 ) n R 8 , OCH 2 C 6 H 5 , OCH 2 C 6 H 4 R 8 and CN;

R 4 , R 5 and R 6 are independently selected from (CH 2 ) n−1 CH 3 , (CH 2 ) n R 8 , CH 2 C 6 H 5 and CH 2 C 6 H 4 R 8 ; wherein R 7 is C 6 H 5 , C 6 H 4 R 9 , SO 3 R 10 or COOR 11 ; R 8 is SO 3 R 10 or COOR 11 ; n and m are integers respectively selected from 1-18 and 0-18; R 9 is arsonic acid, boric acid, carboxylic acid, sulfonic acid, amino, hydroxyl, sulfhydryl or C 1 -C 18 alkyl; R 10 is N(R 12 R 13 R 14 R 15 ); R 11 is a C 1 -C 18 alkyl; R 12 , R 13 , R 14 and R 15 are independently selected from H, C 1 -C 18 alkyl and (CH 2 ) p OH, and p is an integer selected from 0-18; and

Z − is a halide anion or OTs − .

2. A method of preparing the fluorescent dye of claim 1 , comprising:

preparing a compound of formula (III) and Lawesson's reagent;

dissolving the compound of formula (III) and the Lawesson's reagent in a first solvent; and subjecting the reaction mixture to substitution reaction under heating in an inert gas to produce a compound of formula (II); and

subjecting the compound of formula (II) and a nucleophilic reagent R 1 Z to addition reaction to produce the fluorescent dye of formula (I);

wherein X and Y are independently selected from O, S, C(CH 3 ) 2 and NR 6 ;

R 1 is (CH 2 ) n−1 CH 3 , (CH 2 ) n R 7 , (CH 2 ) m C 6 H 5 or (CH 2 ) m C 6 H 4 R 7 ;

R 2 and R 3 are independently selected from H, F, Cl, Br, I, (CH 2 ) n−1 CH 3 , (CH 2 ) n R 8 , CH 2 C 6 H 5 , CH 2 C 6 H 4 R 8 , O(CH 2 ) n−1 CH 3 , O(CH 2 ) n R 8 , OCH 2 C 6 H 5 , OCH 2 C 2 H 4 R 8 and CN;

R 4 , R 5 and R 6 are independently selected from (CH 2 ) n−1 CH 3 , (CH 2 ) n R 8 , CH 2 C 6 H 5 and CH 2 C 6 H 4 R 8 ; wherein R 7 is C 6 H 5 , C 6 H 4 R 9 , SO 3 R 10 or COOR 11 ; R 8 is SO 3 R 10 or COOR 11 ; n and m are integers respectively selected from 1-18 and 0-18; Re is arsonic acid, boric acid, carboxylic acid, sulfonic acid, amino, hydroxyl, sulfhydryl or C 1 -C 18 alkyl; R 10 is N(R 12 R 13 R 14 R 15 ); R 11 is a C 1 -C 18 alkyl; R 12 , R 13 , R 14 and R 15 are independently selected from H, C 1 -C 18 alkyl and (CH 2 ) p OH, and p is an integer selected from 0-18; and

Z − is a halide anion or OTs − .

3. The method of claim 2 , wherein the first solvent is a mixed solution of dichloromethane and anhydrous tetrahydrofuran; and/or

a temperature of the substitution reaction is 40-50° C.; and/or

a temperature of the addition reaction is 25-60° C.; and/or

a molar ratio of the compound of formula (III) to the Lawesson's reagent is 1:1; and/or

a molar ratio of the compound of formula (II) to the nucleophilic reagent R 1 Z is 1:2-5.

4. The method of claim 2 , wherein the compound of formula (III) is prepared by the steps of:

preparing a compound of formula (VI) and a compound of formula (VII);

subjecting the compound of formula (VI) and a nucleophilic reagent R 4 Z to addition reaction to produce a compound of formula (V);

subjecting the compound of formula (VII) and a nucleophilic reagent of R 5 Z to addition reaction to produce a compound of formula (IV);

mixing the compound of formula (V) and the compound of formula (IV) with a squaric acid solution, and reacting the reaction mixture in the presence of a catalyst to obtain the compound of formula (III);

5. The method of claim 4 , wherein a solvent in the squaric acid solution is ethanol; and/or

the catalyst is triethyl orthoformate; and/or

a molar ratio of the compound of formula (V) to the compound of formula (IV) to the squaric acid is 1:(0.8-1.2):(0.8-1.2).