A new perspective on the beryllium sensor platform: Low symmetry phthalocyanine-based molecular design and ultra trace amount Be²⁺ ion recognition in aqueous media

New multichannel sensors based on unsymmetrical phthalocyanines (P—A₃BZnPc (1) and its water-soluble form Q—A₃BZnPc (2)) were developed for Be²⁺ determination in water and THF. The structures of the sensors were elucidated by single-crystal X-ray diffraction and spectroscopic methods such as ¹H- and ¹³C-NMR, IR, MALDI-TOF-MS, UV–vis, and steady-state fluorescence. The sensors (1) and (2) are dual-channel sensors and operate in the NIR region with λ_abs-λ_emm wavelengths of 685 nm –702 nm and 690 nm–706 nm, respectively. The selectivity of the sensors against Be²⁺ was explored in the presence of different metal ions (Li⁺, Na⁺, K⁺, Cs⁺, Mg²⁺, Ca²⁺, Ba²⁺, Al³⁺, Hg²⁺, Ni²⁺, Cd²⁺, Zn²⁺, Fe²⁺, Co²⁺, and Fe³⁺) and no significant interference was reported except Co²⁺, causing an interference only for sensor (2). Limit of Detection (LOD) measurements gave LOD values around 2.9 ppb, which is lower as compared to the threshold value in aqueous solution (4 ppb), determined by the World Health Organization (WHO). The response times of the sensors, estimated by UV–vis and fluorescence spectroscopy techniques, were found to be 0.7 s and 0.6 s, respectively. Owing to these short response times, the sensors can be included in the class of fast sensors when compared with other sensors given in the literature. The results prominently indicate that the sensors developed in this work are highly selective and sensitive to Be²⁺ and have a potential of usage in the detection of Be²⁺ in aqueous media.