Nonlinear properties of chloroindium phthalocyanines with nanosecond pulses

•Tetra-α-(2-ethylbutoxy) and tetra-β-(2-ethylbutoxy) chloroindium phthalocyanines are both excellent optical limiting materials.•Fast response time of the population transfer will promote two-step sequential two-photon absorption.•The position of substituent together with the molecular concentration can strongly influence the molecular optical limiting performance.•Tetra-β-(2-ethylbutoxy) chloroindium phthalocyanine shows better optical limiting characteristics with nanosecond pulses.