Binuclear Ln (III) complexes: High‐efficiency sensing of acetonitrile/dichloromethane and magnetocaloric effect

Abstract

At room temperature, 2-aminomethylpyridine, Ln (NO 3) 3 Á6H 2 O and (E)-2-((3-methoxy-2-oxidobenzylidene)amino)ethanesulfonate (L 1) in methanol and acetonitrile to obtain four complexes: [Ln 2 (L) 2 (NO 3) 4 ] (Ln = Sm (1), Eu (2), Gd (3), Tm (4), and L = (E)-2-methoxy-6-(((pyridin-2-ylmethyl)imino) methyl)phenol). The original organic ligand L 1 and 2-aminomethylpyridine reacted in situ under the catalyzed condition of Ln III ion to form a new Schiff base ligand L. In the above process, firstly, the C = N double bond in the original Schiff base ligand L 1 is broken and further combines with 2-aminomethylpyridine to form a new Schiff base ligand L. As far as we know, this is rare in the formation of lanthanide complexes. When Complex 2 was subjected to luminescence test, it was found to have an extremely high selectivity to acetonitrile (CH 3 CN) and methylene chloride (CH 2 Cl 2). Therefore, after screening a variety of different organic solvents, here we explore a method that can quickly and efficiently respond to CH 3 CN/CH 2 Cl 2. In addition, we can visually distinguish the response of Complex 2 to multiple volatile organic compounds (VOCs). The magnetocaloric effect (MCE) test of Complex 3 showed 18.7 JÁkg −1 ÁK −1 at 2 K for ΔH = 5 T.

Exploring the functional relation of magnetic density and magnetocaloric effect based on a dinuclear system

“…For the Gd 2 , the largest values of −Δ S m are 29.96 J kg −1 K −1 at 2 K and 7 T, which is smaller than the expected maximum −Δ S m (32.17 J kg −1 K −1 ) calculated as 2 R ln(2 S + 1) ( R = 8.3145 J mol −1 K −1 , S = 7/2) for two uncoupled Gd (III) ions. [ 66–68 ] The differences between the theoretical and observed values of −Δ S m can be attributed to the presence of antiferromagnetic interactions between the Gd (III) ions. The value of 29.96 J kg −1 K −1 is higher than most reported dinuclear complexes of antiferromagnetic coupling except a value of 31.33 J kg −1 K −1 (Table 2).…”

“…The magnetic entropy change values (−Δ S m ) of Gd 2 , Gd 0.24 Y 1.76 , Gd 0.51 Y 1.49 , Gd 1.04 Y 0.96 , and Gd 1.46 Y 0.54 were calculated for various fields and temperatures from magnetization data by using the Maxwell equation −Δ S m ( T ) = ʃ [∂ M ( T , H )/∂ T ] H d H (Figure 5). [ 66,67 ] According to the Maxwell equation, the plots of −Δ S m versus T are shown in Figure 5e. For the Gd 2 , the largest values of −Δ S m are 29.96 J kg −1 K −1 at 2 K and 7 T, which is smaller than the expected maximum −Δ S m (32.17 J kg −1 K −1 ) calculated as 2 R ln(2 S + 1) ( R = 8.3145 J mol −1 K −1 , S = 7/2) for two uncoupled Gd (III) ions.…”