Selective Luminescent Chemosensing of Chloride Based on a Cyclometalated Platinum(II) Complex in Water: Crystal Structures, Spectroscopic Studies, Extraction, and Bioimaging

Abstract

Selective anion sensing by luminescent chemosensors capable of operating in aqueous conditions is a central field of modern supramolecular chemistry that impacts analytical and biological chemistry. A cationic cyclometalated [Pt(N^C^N)NCCH3]OTf complex, 1 [N^C^N = 1,3-bis(1-(p-tolyl)-benzimidazol-2′-yl)benzene, OTf = triflate], was prepared, structurally described by single-crystal X-ray diffraction and studied in-depth as a luminescent chemosensor for anions in aqueous phase and solid state. A series of related neutral [Pt(N^C^N)X] complexes (X = Cl, 2; CN, 3 and I, 4) were formed readily upon treatment of 1 with the respective NaX salt in aqueous media and were described structurally by X-ray diffraction. Complex 1 is hydrostable with phosphorescent green emission originated by intraligand transitions, and [d yz (Pt) → π*(N^C^N)] charge transfer transitions, as evidenced by TD-DFT calculations and lifetime. Additions of halides, pseudohalides, oxyanions, and dicarboxylates to a neutral aqueous solution of 1 modified its green emission intensity with a pronounced affinity (K = 1.5 × 105 M–1) and turn-on signal toward Cl– within the micromolar concentration range. Pt complex 1 is two orders of magnitude more selective for Cl– than the other halides, CN– and basic oxyanions. Such Cl– affinity for a metal-based chemosensor in aqueous media is still rare. On the basis of X-ray crystallographic analysis and multiple spectroscopic tools (NMR, UV–vis, luminescence, MS, lifetimes) the origin of this selectivity hinges on the cooperative three-point recognition involving one coordination bond (Pt–Cl) and two convergent short C–H···Cl– contacts. This strong affinity and efficient optical response can be utilized in quantitative Cl– sensing in real samples and solid–liquid extractions. Additionally, chloro-Pt complex, 2 may be relevant to bioimaging as a marker for cell nuclei, as revealed by its emission within living cells and intracellular distribution by confocal microscopic studies. These results demonstrate the usefulness of the new water-stable luminescent Pt-N^C^N complexes as effective analytical tools in anion sensing and extraction agents.

Nonlinear and Emissive {[MIII(CN)6]3–···Polyresorcinol} (M = Fe, Co, Cr) Cocrystals Exhibiting an Ultralow Frequency Raman Response

“…The hydrogen-bonded MDiR architecture revealed the dmp topology (Figure S9), whereas among the hydrogen-bonded MTriRB architectures two separate topologies are distinguished: CrTriRB (Cc space group) revealed rather the rare neb topology, while FeTriRB (P2 1 2 1 2 space group) and CoTriRB (P2 1 space group) showed the frequently encountered dia topology (Figure S10). Consistently, CrTriRB includes 6 6 topological motifs, which differ from the 6 4 motifs noted for FeTriRB and CoTriRB (Figure S10c). 59 DFT Study on Hydrogen Bonding Interactions.…”

“…Optical properties of matter based on nonlinear response and/or photoluminescence have attracted strong interest in fields such as bioimaging, − anticancer therapy, or multifunctional molecular materials for photonic application, e.g . toward optical modulation of light and for luminescent thermometry. , The phenomenon known as second-harmonic generation (SHG) has been extensively researched and utilized due to its ability to convert two incident photons into a single emitted photon with a doubled frequency.…”

“…hyperpolarizability, and tectonic character that allows for the desired supramolecular organization through noncovalent interactions. ,,, For example, hydrogen-bonded synthons are exploited in directional and cooperative extension toward supramolecular architectures, − especially if one combines multisite complementary H-bond donor and acceptor or/and slightly modifies the already established contacts via judicious molecular replacement. , The effective self-assembly process is usually supported by other ubiquitous weak interactions (π···π, ion···π, C–H···π, etc.). The potential of such a strategy was illustrated by the acquisition of materials that fulfill the technological demands for SHG performance competitive with the traditional ones ( see above ) as well as by efficient enantiospecific molecular recognition toward enantiopure crystal growth. ,− Moreover, a hybrid approach involving 3d and 4f metal ion coordination complexes and their salts allows for the introduction of other functions, such as anion binding, , specific luminescence for ratiometric or thermometric performance, , single-ion magnetic properties for ultrahigh density data recording, storage, and processing, , or switchable structural and dielectric loss properties owing to the phase transitions inscribed in the structure of molecular fragments and their positioning in the crystal, as commonly observed in molecular hybrid perovskites. − In parallel, phonon properties of molecular materials have been studied by terahertz (THz) spectroscopy ,− in the context of the optimization of their luminescent response (“management” of nonradiative vibrational loss) , and slow magnetic relaxation (“management” of the effective energy barrier) or the generation of the THz signal through optical stimulation …”

“…The potential of such a strategy was illustrated by the acquisition of materials that fulfill the technological demands for SHG performance competitive with the traditional ones ( see above ) as well as by efficient enantiospecific molecular recognition toward enantiopure crystal growth. 15 , 32 − 35 Moreover, a hybrid approach involving 3d and 4f metal ion coordination complexes and their salts allows for the introduction of other functions, such as anion binding, 4 , 23 specific luminescence for ratiometric or thermometric performance, 8 , 9 single-ion magnetic properties for ultrahigh density data recording, storage, and processing, 8 , 9 or switchable structural and dielectric loss properties owing to the phase transitions inscribed in the structure of molecular fragments and their positioning in the crystal, as commonly observed in molecular hybrid perovskites. 36 − 39 In parallel, phonon properties of molecular materials have been studied by terahertz (THz) spectroscopy 9 , 40 − 42 in the context of the optimization of their luminescent response (“management” of nonradiative vibrational loss) 43 , 44 and slow magnetic relaxation (“management” of the effective energy barrier) 45 or the generation of the THz signal through optical stimulation.…”

Shining New Light on Biological Systems: Luminescent Transition Metal Complexes for Bioimaging and Biosensing Applications

“…Dorazco-Gonzaĺez and co-workers have also developed a cyclometalated platinum(II) complex (348) for selective sensing of Cl − . 631 The Cl − recognition involves the formation of a Pt−Cl bond and two convergent C−H•••Cl interactions, which rigidify the complex and induces emission enhancement. The cooperative three-point recognition results in higher binding affinity and selectivity toward Cl − (K b = 1.5 × 10 5 M −1 ) over other halide ions (K b = 5.75 × 10 2 , 3.67 × 10 3 , and 1.42 × 10 4 M −1 for F − , Br − , and I − , respectively).…”