Dipicolylamine-Based Fluorescent Probes and Their Potential for the Quantification of Fe³⁺ in Aqueous Solutions

Abstract

We have synthesized two ligand systems, N(SO 2 )(R 1 )dpa (L1) and N(SO 2 )(R 2 )dpa (L2), where R 1 = biphenyl and R 2 = azobenzene, which are sulfonamide derivatives of the NNN-donor chelating dipicolylamine. Both L1 and L2 can be used as sensors for detecting Fe 3+ and are highly sensitive and selective over a wide range of common cations. Time-dependent density functional theory (TDDFT) calculations confirmed that the key excitations of L2 and the [Fe(L2)(H 2 O) 3 ] 3+ model complex involve −R 2 -unit-based π and π* charge transfer. L2 demonstrates a relatively high photostability, a fluorescence turn-on mechanism, and a detection limit of 0.018 μM with 1.00 μM L2 concentration, whereas L1 has a detection limit of 0.67 μM. Thus, both ligands have the potential to be used as fluorosensors for the detection of Fe 3+ in aqueous solutions.

Spray-On Colorimetric Sensors for Distinguishing the Presence of Lead Ions

“…Another notable outcome in this work is the observation that the color response to Pb(NO 3 ) 2 was four times greater than any other anion or cation tested, all of which remained at the threshold of being visually undetectable. It is interesting to see the high degree of selectivity here when compared with reports that dipicolylamine is capable of binding with Pb 2+ , Fe 3+ , Zn 2+ , and K + [20,28,30,31]. While we do see in our study that Zn 2+ and K + give the next highest color response, they are still at a low CIELab colorspace distance of ~10 which is almost not visible at the 0.1 mM concentration examined.…”

“…Various dipicolylamine-containing sensing systems have been implemented for detection of metal ions, due to the ability of the pyridyl arms of this ligand to bind with Pb 2+ , Fe 3+ , Zn 2+ , and K + [28,31]. Here, we utilize a dipicolylamine-terminated diacetylene-containing amphiphile, which has previously been shown to work in liquid-phase liposomal sensing systems, for the specific detection of lead ions [20,21].…”

“…Synthesis of dipicolylamine-terminated diacetylene-containing amphiphile in this work follows a modification of previous reports and is depicted in Figure 2 [30,31]. Unless otherwise noted, reagents were obtained from Sigma Aldrich Co. (St. Louis, MO, USA).…”

Alendronate-Modified Polydiacetylene (PDA) Dual-Mode Sensor for the Selective Detection of Lead(II) Ions up to the nM Level in Solutions and Agarose Films

“…57 However, the dipicolyl unit has been reported to form a complex with other metal ions such as Fe 3+ and Zn 2+ , compromising the selectivity of the sensing system. 63,64 Likewise, PDA-based probes incorporating aza-crown ether 58 and thymine-1-acid 59 as the recognition unit for Pb 2+ ions exhibit similar limitations due to the possibility of complex formation with various other metal ions. 65−67 Other PDAbased probes often exhibit poor sensitivity or require an expensive solid matrix for solid-phase sensing.…”

“…PDA-based colorimetric sensors are also designed for the detection of Pb 2+ ions (Figure ). − For example, Yoon and co-workers reported a dipicolyl amine-modified PDA probe for the detection of Pb 2+ ions . However, the dipicolyl unit has been reported to form a complex with other metal ions such as Fe 3+ and Zn 2+ , compromising the selectivity of the sensing system. , Likewise, PDA-based probes incorporating aza-crown ether and thymine-1-acid as the recognition unit for Pb 2+ ions exhibit similar limitations due to the possibility of complex formation with various other metal ions. − Other PDA-based probes often exhibit poor sensitivity or require an expensive solid matrix for solid-phase sensing. Molecules bearing phosphate group exhibit a strong affinity for lead ions and are frequently utilized in the detection and removal of lead ions. , Herein, we report the design and development of a selective and sensitive sensor for Pb 2+ ions based on the high affinity of lead ions with a phosphate group.…”