Family of Chiral Zn^II–Ln^III (Ln = Dy and Tb) Heterometallic Complexes Derived from the Amine–Phenol Ligand Showing Multifunctional Properties

Abstract

A family of chiral 3d−4f heterometallic complexes, namely, [Zn 2 Ln(R,R-L) 2 (H 2 O) 4 ](ClO 4 ) 3 ) [Ln = Dy (1), Tb ( 3 5), Tb (7)], and [Zn 2 Ln 2 (S,S-L) 2 (CO 3 ) 2 (NO 3 ) 2 ]•2CH 3 OH [Ln = Dy (6), Tb (8)] {H 2 L = cyclohexane-1,2-diylbis(azanediyl)bis-(methylene)bis(2-methoxyphenol)}, has been synthesized and characterized. Crystal structure analysis reveals that complexes 1− 4 are isostructural trinuclear clusters crystallized in chiral space group C2 2 2 1 , and 5−8 are isostructural tetranuclear clusters crystallized in chiral space group P1. Interestingly, the adjacent [ZnLn] units within the tetranuclear cluster in 5−8 are bridged by two carbonate anions via in situ incorporation of CO 2 from air. Magnetic measurements indicate that complexes 1 and 3 exhibit field-induced single-molecule magnet behavior with energy barriers (U eff ) of 22.46 and 38.70 K (or 41.87 K), respectively. Complex 5 displays typical SMM behavior with U eff = 19.61 K under zero dc field, while for complex 7, no obvious out-of-phase signals are observed even under 2 kOe dc field, the absence of SMM behavior. The solid-state luminescence studies reveal that all complexes display the characteristic fluorescence emission of lanthanide ions. Furthermore, the Kurtz−Perry measurements reveal these complexes are potential nonlinear optical materials.

CO2‐fixation into carbonate anions for the construction of 3d‐4f cluster complexes with salen‐type Schiff base ligands: from molecular magnetic refrigerants to luminescent single‐molecule magnets

“…For example, the carbonate ligand was recently introduced into chiral Zn‐Ln Schiff base heterometallic SMMs, which improved the fluorescence of Tb (III) ions by replacing the terminal coordination water molecules. [ 12 ] In this work, the carbonate ligand also prevents the possibility of terminal coordination of water molecules on the Tb (III) ion, so the Tb (III) ion of compounds 3 and 4 also have clear fluorescence. On the other hand, our recent research indicates that the length of the diimine chain on salen ligands has an effect on the fluorescence of Zn 2 Dy 2 ‐salen SMMs, [ 11 ] this work confirms that this factor also affects the fluorescence of Zn 2 Tb 2 ‐salen SMMs.…”

“…Notably, such Zn 2 Ln 2 cluster structures are reminiscent of other carbonate‐bridged Zn 2 Dy 2 SMMs derived from Schiff bases. [ 3d,e,12 ]…”

“…The Zn 2 Tb 2 complexes 3 and 4 have characteristic fluorescence of the Tb (III) ions, just like another carbonate‐bridged cluster complex [Zn 2 Tb 2 (R,R‐L) 2 (CO 3 ) 2 (NO 3 ) 2 ]·2CH 3 OH . [ 12 ] As shown in Figure 9, the room temperature solid‐state emission spectra excited at 350 nm of both 3 and 4 show four typical emission bands of Tb (III) ions corresponding to 5 D 4 → 7 F 6 , 5 D 4 → 7 F 5 , 5 D 4 → 7 F 4 and 5 D 4 → 7 F 3 transitions, which have respective peaks at 441, 542, 584 and 622 nm for 1 , and at 439, 542, 585 and 624 nm for 2 . Among them, the emission band caused by the 5 D 4 → 7 F 5 transition in the green light region is the strongest, so the two compounds display green fluorescence.…”

“…[ 10 ] In addition, the Zn (II) Schiff base building block along with a suitable bridging ligand can have an antenna effect on the emission of lanthanide (III) ions, and thus form luminescent SMMs. [ 11 ] Carbonate is such a suitable bridging ligand as shown by a very recent research, [ 12 ] and we used to obtain carbonate‐bridged SMM and cryogenic molecular magnetic refrigerant through carbon dioxide fixation. [ 9c ] Recently, we obtained six new carbonate‐bridged Zn 2 Ln 2 cluster complexes derived from salen‐type Schiff base ligands through carbon dioxide fixation in the air, Zn 2 Dy 2 ( μ 3 ‐CO 3 ) 2 (L a ) 2 (NO 3 ) 2 (MeOH) 2 [ 1 , H 2 L a = N , N ′‐ bis(3‐methoxysalicylidene)‐ 1,3‐diaminopropane], [Zn 2 Dy 2 ( μ 3 ‐CO 3 ) 2 (L b ) 2 (NO 3 ) 2 ]·2MeOH [ 2 , H 2 L b = N , N ′‐ bis(3‐methoxysalicylidene)‐ 1,2‐diaminoethane], Zn 2 Tb 2 ( μ 3 ‐CO 3 ) 2 (L a ) 2 (NO 3 ) 2 (MeOH) 2 ( 3 ), [Zn 2 Tb 2 ( μ 3 ‐CO 3 ) 2 (L b ) 2 (NO 3 ) 2 ]·2MeOH ( 4 ), [Zn 2 Gd 2 ( μ 3 ‐CO 3 ) 2 (L a ) 2 (NO 3 ) 2 ]·2MeOH ( 5 ), and [Zn 2 Gd 2 ( μ 3 ‐CO 3 ) 2 (L b ) 2 (NO 3 ) 2 ]·2MeOH ( 6 ).…”

Isocyanate Insertion into a La–P Phosphide Bond: A Versatile Route to Phosphaureate-Bridged Heterobimetallic Lanthanide–Coinage-Metal Complexes

“… 4 , 6 , 32 − 35 In this context, transition metals such as iron(0/II/III), 36 − 43 nickel(II), 44 − 47 and zinc(II) 45 , 48 , 49 have been used to influence the magnetic behavior of lanthanide compounds, whereas e.g. iridium(III), 50 rhenium(I), 51 platinum(II), 51 − 54 palladium(II), 54 zinc(II), 48 , 55 gold(I), 54 , 56 , 57 and silver(I) 54 have been introduced for efficient sensitizing of lanthanide luminescence 58 − 60 in heterobimetallic or -trimetallic systems. Despite these significant advances, straightforward and rational designs of heterobimetallic lanthanide–coinage-metal complexes in particular have not been much developed as yet.…”