Cyanine-derived compound, preparation method therefor, and application thereof

A cyanine derivative, having a structure represented by formula (1):

• wherein
• X is selected from —O— or —NH—;
• Z is selected from —C(O)— or —(CH2)m—;
• Y− is a biocompatible anion bromine ion, a chlorine ion, or an acetate ion;
• R1, R2, R3, and R4 are selected from hydrogen, halogen, substituted or unsubstituted C1-20 alkyl, substituted or unsubstituted C1-20 alkoxy, substituted or unsubstituted C6-30 aryl, C1-20 ester, or sulfonate, or any two adjacent groups of R1, R2, R3, and R4, together with a carbon atom bonded thereto, form an unsubstituted or substituted C3-10 aliphatic ring, C6-30 aromatic ring or C1-30 heteroaromatic ring, wherein a substituent is selected from halogen, alkyl, and alkoxy;
• n is an integer not less than 1;
• k is an integer of 1-3;
• and
• m is an integer of 1-6.