Near-Infrared Luminescent and Magnetic Cyano-Bridged Coordination Polymers Nd(phen)_n(DMF)_m[M(CN)₈] (M = Mo, W)

Abstract

T he design and study of multifunctional molecular materials exhibiting different physical properties have attracted a great deal of attention because of their fundamental interest and their potential applications. 1 Efforts have been focused on investigations of magnetoluminescent coordination polymers 2 and, in particular, those presenting luminescence in the near-infrared (NIR) region because of interesting applications in fields ranging from biomedical applications to telecommunications. 3 Along this line of thought, one of the promising families of coordination polymers is cyano-bridged networks in which the luminescent lanthanide ions are associated with nd (n = 3À5) cyanometallate building blocks in order to enhance magnetic anisotropy and magnetic interactions. 4 Indeed, numerous one-, two-, and threedimensional cyano-bridged compounds presenting mainly magnetic properties have been reported in the last 30 years, 5 but the luminescent properties of these compounds have rarely been exploited. 6 To the best of our knowledge, only two compounds based on an association of NIR-emissive lanthanides (Yb 3+ and Nd 3+ ) with cyanometallates have been reported, but the diamagnetism of the transition-metal ions results in the absence of magnetic interactions. 7 Our strategy to obtain magnetoluminescent materials relies on associating paramagnetic [M(CN) 8 ] 3À (M = Mo, W) building blocks (which do not act as luminescence quenchers, contrary to most of the hexacyanometallates) with an NIR-emissive Nd 3+ coordinated to an antenna ligand in order to enhance luminescence. In this Communication, we report the first examples of the NIR-emissive one-dimensional cyano- (Figures 1 and 2). Besides the common bridging cyanide group, while in compound 1 the Nd 3+ center is coordinated to two N,N 0 -chelated phenanthroline molecules and two DMF and one water solvent moieties (Figure 1c), in compounds 2 and 3, the coordination sphere is filled instead with DMF molecules (five in total) and only one phenanthroline molecule (Figure 2b).Because the five spatially close DMF molecules seem to impose a significant steric impediment around the Nd 3+ coordination environment, ∞ 1 [Nd(phen)(DMF) 5 W(CN) 8 ] (in 3) deviates more from linearity than that present in 1 (Figures 1a and 2a). Close packing of individual polymers to produce the crystal structures of 1À3 is clearly mediated by various supramolecular interactions, namely, close πÀπ contacts (Figures S1 and S2 in the SI) and OÀH 3 3 3 (N,O) hydrogen-bonding interactions. Because of the extra phenanthroline molecule in 1, the number of πÀπ contacts is also significantly higher than that in 2 and 3, with offset contacts occurring parallel to both the a and b axes of the unit cell ( Figure S1 in the SI). In addition, the

Thermal switching between blue and red luminescence in magnetic chiral cyanido-bridged EuIII–WVcoordination helices

“…1 Several Ln III -[M V (CN) 8 ] (Ln = lanthanide, M = Mo, W) systems were characterized. [6][7][8][9] The visible luminescence was shown only for {[M III (H 2 O) 5 ][M V (CN) 8 ]} (M III = Eu, Tb, Eu-Gd = 1 : 1, Eu-Tb = 1 : 1, Tb-Sm = 1 : 1; M V = Mo, W) layers, whereas the near infrared for one-dimensional {[Nd(phen) 2 (dmf) 2 (H 2 O)][Mo(CN) 8 ]}?2H 2 O and {[Nd(phen)(dmf) 5 ][M(CN) 8 ]}?xH 2 O (M = Mo, W; phen = 1,10phenanthroline, dmf = N,N9-dimethyl-formamide) polymers was observed. 7,9 In this context, we combined highly luminescent Eu 3+ and paramagnetic [W V (CN) 8 ] 32 ions.…”

“…[6][7][8][9] The visible luminescence was shown only for {[M III (H 2 O) 5 ][M V (CN) 8 ]} (M III = Eu, Tb, Eu-Gd = 1 : 1, Eu-Tb = 1 : 1, Tb-Sm = 1 : 1; M V = Mo, W) layers, whereas the near infrared for one-dimensional {[Nd(phen) 2 (dmf) 2 (H 2 O)][Mo(CN) 8 ]}?2H 2 O and {[Nd(phen)(dmf) 5 ][M(CN) 8 ]}?xH 2 O (M = Mo, W; phen = 1,10phenanthroline, dmf = N,N9-dimethyl-formamide) polymers was observed. 7,9 In this context, we combined highly luminescent Eu 3+ and paramagnetic [W V (CN) 8 ] 32 ions. To introduce chirality and enhance luminescence, we applied a chiral Pybox (Pybox = pyridine-bis(oxazoline)) derivative which was shown to be an efficient sensitizer for Eu III .…”

Lanthanide Photoluminescence in Heterometallic Polycyanidometallate-Based Coordination Networks

“…The trimetallic [Eu III 0.5 Tb III 0.5 (H 2 O) 5 ] [W V (CN) 8 ] framework exhibits both red Eu 3+ and green Tb 3+ emission peaks realized by the LMCT, O-Eu or W-related, excitation, and the additional Tb 3+ -to-Eu 3+ intermetallic energy transfer occurring through the [W V (CN) 8 ] 3− moieties [103]. The emission of Nd 3+ was also possible to detect within the family of octacyanidometallate-based materials, as reported for the cyanido-bridged [Nd III (phen) 2 (dmf) 2 (H 2 O)][Mo V (CN) 8 ]·2H 2 O and [Nd III (phen)(dmf) 5 ][M V (CN) 8 ]· x H 2 O (M = Mo, W; phen = 1,10-phenanthroline) chains showing NIR emission of 4f metal ion sensitized by phen ligand [104]. …”

“…It enables the observation of visible and NIR photoluminescence of accompanying emissive chromophores [32]. In effect, a considerable number of photoluminescent d–f coordination networks based on octacyanidometallates were reported (Figure 7 and Figure 8, Table 4) [101,102,103,104,105,106,107,108,109,110]. In the aqueous solution, trivalent lanthanide(3+) and [M V (CN) 8 ] 3− ions produce the cyanido-bridged [Ln III (H 2 O) 5 ][M V (CN) 8 ] (Ln = Sm, Eu, Gd, Tb; M = Mo, W) layered frameworks of a square grid topology [101,102,103].…”

The synthesis, crystal structure and magnetic properties of a one-dimensional terbium(III)–octacyanidomolybdate(V) assembly

“…Among these compounds, there are only a few based on anionic octacyanidomolybdate(V) with rare earth ions, viz. [Tb III -(pzam) 3 (H 2 O){Mo V (CN) 8 }]ÁH 2 O (pzam is pyrazine-2-carboxamide; Prins et al, 2007), {[Yb III (bpy) 2 (DMF)(H 2 O)]-[Mo V (CN) 8 ]Á0.5bpyÁ4.5H 2 O} n (bpy is 2,2 0 -bipyridinyl and DMF is dimethylformamide; Ma et al, 2010), [Ln(CH 3 CN) 2 -(H 2 O) 4 ][Mo(CN) 8 ]ÁCH 3 CN (Qian et al, 2010), [Pr(tmphen)-(DMF) 5 ][M(CN) 8 ]ÁDMFÁ2H 2 O (tmphen is 3,4,7,8-tetramethyl-1,10-phenanthroline; M = W, Mo; Qian et al, 2011), Nd (phen) n (DMF) m [Mo(CN) 8 ] (phen is 1,10-phenanthroline; Long et al, 2011) and [Ln III (DMF) 6 Mo V (CN) 8 ] n (Ln = Pr, Nd, Sm, Eu, Gd, Ho, Er, Tm, Yb;Tong et al, 2013).…”