A new highly Selective, sensitive and NIR spectrophotometric probe based on A₂B₂-Type of unsymmetrical phthalocyanine for hazardous Be²⁺ recognition

The aim of this work is to construct a new A₂B₂-type of unsymmetrical and ratiometric phthalocyanine (Pc) based-probe O-A₂B₂ZnPc to provide an effective solution to critical inadequacy to be experienced for the detection of hazardous Be²⁺. O-A₂B₂ZnPc enabling strong absorption and emission in Near-Infrared region (λ_abs-λ_em wavelengths of 694-712 nm) showed excellent selectivity and sensitivity toward Be²⁺ among competitive metal ions by both spectrophotometric and fluorometric methods. The probe with oligomeric Pc form in THF was degraded with the addition of aqueous Be²⁺ and arranged to J-aggregation form, resulting in a remarkably diminishing in Q-band at 694 nm as well as a new band formation at 746 nm, and a considerably decreasing in fluorescence emission. The probe has superior features for the determination of Be²⁺ such as high quantum efficiency and photochemical stability, rapid response (1 s), high selectivity and very low Limit of Detection (0.26 ppb and 1.5 ppb) for UV-Vis and fluorescence, respectively which are quite good values according to the permissible amount of Be²⁺ (4 ppb) in water as specified by World Health Organization. O-A₂B₂ZnPc can be shown among the best performing probes with its unique properties according to previous studies in the literature. In addition, the geometrical and spectral features of the O-A₂B₂ZnPc were analyzed in detail by DFT calculations.