Quenching of Fluorescence in Bodipy‐Derived Trifluoromethyl Enaminone Ligands upon Coordination to Copper(II)

Abstract

The synthesis of two trifluoromethyl‐derived enaminone ligands, L1H (bidentate) and L2H2, (tridentate), which bear a fluorescent 4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene (Bodipy) moiety, leads to the preparation and characterization of two CuII complexes {[Cu(L1)2]·2(CH2Cl2) (A) and [Cu4(L2)4]·4(C4H8O2) (B)} that exhibit different architectures. The magnetic properties of the cubane‐like complex B evidence a dominant ferromagnetic behavior characterized by exchange coupling constants J1 = +20.56(3) cm–1 and J2 = –10.29(2) cm–1. Indeed, whereas the luminescence properties of the Bodipy‐derived trifluoromethyl enaminones L1H and L2H2 are typical of the Bodipy skeleton, the emission is totally quenched in both mononuclear (A) and cubane (B) CuII complexes. To elucidate this quenching phenomenon, the Rehm–Weller equation has been used based on experimental cyclic voltammetry redox potential measurements. The result remains ambiguous for complexes A and B, and the origin of the quenching phenomenon, photoinduced electron transfer (PET) versus energy transfer (Förster or Dexter), cannot be deduced.

[12]aneN3-based BODIPY as a selective and sensitive off–on sensor for the sequential recognition of Cu2+ ions and ADP

“…Obviously, compound 1 showed excellent selectivity for Cu 2+ over other metal ions. The quench of fluorescence can be attributed to the photo-induced electron transfer (PET) mechanism caused by Cu 2+ ions [32,33].…”

Resonance‐Assisted Hydrogen Bonding as a Driving Force in Synthesis and a Synthon in the Design of Materials

“…[150][151][152] They have been extensively used as key intermediates in organic synthesis [153][154][155] and as ligands in coordination chemistry, [156][157][158] and can be synthons in bioactive natural products. [150][151][152] They have been extensively used as key intermediates in organic synthesis [153][154][155] and as ligands in coordination chemistry, [156][157][158] and can be synthons in bioactive natural products.…”

“…[153][154][155][156][157][158][173][174][175][176] RAHB-assisted synthesis of b-enaminones by condensation affords an unique product only in the case of symmetrical b-diketones or when the two carbonyl groups show av ery different electrophilicity towards the nucleophile amine. The Z and E isomers of b-enaminones exhibit different chemical reactivities in synthetic and coordination chemistry.…”

“…Owing to a RAHB system, β‐enaminones and β‐enamino esters are very stable compounds and can be easily prepared, starting from cheap and easily available starting materials . They have been extensively used as key intermediates in organic synthesis and as ligands in coordination chemistry, and can be synthons in bioactive natural products . β‐Enaminones are related to β‐diketones, containing the RAHB system described in Scheme .…”

3-[Bis(pyridin-2-ylmethyl)amino]-5-(4-carboxyphenyl)-BODIPY as Ratiometric Fluorescent Sensor for Cu2+

“…The introduction of a cation receptor at the 3- and/or 5- position(s) of BODIPY can therefore be used to create a ratiometric fluorescent sensor [ 8 , 9 , 10 , 11 , 12 , 13 ]. However, the development of a ratiometric fluorescent sensor for Cu 2+ is difficult, because Cu 2+ often shows fluorescence quenching with many fluorescent sensors, because of its paramagnetic nature [ 14 , 15 , 16 ]. In our previous study, we synthesized four types of 3-[bis(pyridin-2-ylmethyl)amino]-BODIPYs with bis(pyridin-2-ylmethyl)amine [di(2-picolyl)amine] as the cation receptor at the 3-position of BODIPY [ 17 ].…”