Two novel multifunctional chromic compounds: Synthesis, photochromism, ammonia sensing, and anion sensing.

• Two new compounds were synthesized. • These two compounds can be used to detect Cr 2 O 7 2−. • Compound 2 exhibits ammonia sensing properties. Two new Zn (II)-viologen chromic compounds, named {[(4-BCBPY) 0.5 (HIPA)]·H 2 O} n (1) and {[Zn 3 (IPA) 4 (4-BCBPY)]·2H 2 O} n (2) (4-BCBPY2+ = 1,1′-bis(4-cyanobenzyl)-4,4′-bipyridinium dication, H 2 IPA = isophthalic acid) have been synthesized through varying reaction conditions. Structural analysis reveals that compound 1 possesses a supramolecular compound, while compound 2 exhibits a metal-organic framework (MOF) structure built from trinuclear metal building units. Under the irradiation of a 300 W Xe lamp, compound 1 undergoes a color change from orange to brown, while compound 2 transitions from yellow to green. The introduction of metal ions in compound 2 enhances its light response rate compared to compound 1. Additionally, compound 2 displays a visible color change in the presence of ammonia, whereas compound 1 does not exhibit this capability. Meanwhile, the stable product 2P of 2 was obtained through irradiation, and the structural differences between 2 and 2P were analyzed. Furthermore, the study of time-dependent density functional theory (TDDFT) provides theoretical support for understanding the properties of 1 and 2. Both compounds exhibit intriguing photomodulated luminescence properties and demonstrate remarkable sensing abilities toward Cr 2 O 7 2−. Notably, the introduction of metal ions was found to modulate the photochromic behavior as well as the ammonia/anion sensing properties of these compounds. Two new chromic compounds named {[(4-BCBPY) 0.5 (HIPA)]·H 2 O} n (1) and {[Zn 3 (IPA) 4 (4-BCBPY)]·2H 2 O} n (2) were synthesized from 1, 1 '-bis (4-cyanobenzyl)-4, 4′-bipyridinium and 1, 3-phthalic acid. Compound 1 showed a color change from orange to brown under light irradiation, and the compound 2 showed a color change from yellow to green. The two compounds were used as fluorescence sensors for the detection of Cr 2 O 7 2−. It has good stability and low detection limit for Cr 2 O 7 2−. [Display omitted] [ABSTRACT FROM AUTHOR]