The present disclosure relates to chemical dyes useful for staining and imaging of cells. In particular, the disclosure relates to compound of Formula I, method of preparation thereof, and it's use as a fluorescent probe for staining and/or imaging mitochondria in cells, tissues or animals, resulting in a range of applications including, but not limiting, to sensing local ordering or viscosity of mitochondria, tracking mitochondrial mobility, comparing & evaluating mitochondrial function, local ordering, microviscosity and dynamics. Said dyes have additional advantages including, but not limiting, to low toxicity, longer shelf-life, generate little or no reactive species upon long term light irradiation and do not perturb the functionality of the mitochondria in cells compared to prior art dyes.