The first example of Tb₃-containing metallopolymer-type hybrid materials with efficient and high color-purity green luminescence

Abstract

Ln = Tb, 3 or Ln = Gd, 4) self-assembled from the allyl-modified benzimidazole-type ligand HL (4-allyl-2-(1H-benzo[d]imidazol-2-yl)-6-methoxyphenol) and LnCl 3 ·6H 2 O, a suitable energy level match endows efficient green luminescence (Φ overall = 72%) of Tb 3 -arrayed complex 3. The copolymerization between each of these complex monomers 1-4 and CvC-containing MMA (methyl methacrylate) or NBE (norbornene) shows that degradative chain transfer of the terminal four flexible allyl groups within restrains their radical polymerization with MMA while it does not hinder their effective ring-opening metathesis polymerization (ROMP) with NBE. Thus, two kinds of PMMA-supported doping hybrid materials 1@PMMA, 2@PMMA, 3@PMMA and 4@PMMA and PNBE-supported metallopolymer-type hybrid materials Poly-(NBE-1), Poly(NBE-2), Poly(NBE-3) and Poly(NBE-4) are obtained, respectively. Especially for both 3@PMMA and Poly(NBE-3) with high color-purity characteristic green emission of Tb 3+ ions, improved physical properties including significantly enhanced luminescence (Φ overall = 76% or 83%) are observed, and covalent-bonding endows a higher-concentration self-quenching as compared to physical doping.

Dye-functionalized polymers via ring opening metathesis polymerization: principal routes and applications

“…Alternatively, a labeled ROMP initiator can be prepared in situ by carbene exchange with a terminal olefin, subsequently followed by polymerization, which has been shown for a terbium coordination compound [12].…”

Covalently-bonded grafting of [Ln3(Benzimidazole)4]-arrayed (Ln = Tb, Nd, Yb or Er) complex monomers into PNBE (poly(norbornene)) with highly luminous color-purity green-light or efficient NIR luminescence

“…Moreover, the strong color-purity green-light of complex monomer 3 is also validated from its long lifetime (t obs ) of 158 ms and high overall quantum yield (F Tb L ) of 76%, whereas the better NIR luminescence (t obs ¼ 1.98 ms and F Nd L ¼ 0.53% for 4; t obs ¼ 24.62 ms and F Yb L ¼ 1.28% for 5) of complex monomer 4e5 than that (t obs ¼ 3.21 ms and F Er L ¼ 0.014%) of complex monomer 6 is also realized. Noticeably, the more excellent color-purity green-light performance of complex monomer 3 than that (t obs of 104.54 ms and F Tb L of 72%) of the Cl-À dependent {Tb 3 (L) 4 Cl 4 (MeOH)(H 2 O)$Cl} compound [17] with the same HL ligand, should be attributed to the avoidance of OH-vibrational oscillators [11] directly around the three Tb 3þ ions. As to the relatively larger NIR quantum efficiency (F Yb L ¼ 1.28%) of 5 than that (F Nd L ¼ 0.53%) of 4, it could probably be arisen from heavier luminescent quenching [23] of the two lower energy states ( 4 I 11/2 and 4 I 13/2 ) of Nd 3þ ion by distant CeH and NeH oscillators of the HL ligands.…”

“…The information on the starting materials and the determination methods, and the synthesis of the allyl-modified benzimidazole ligand HL with an improved procedure from the literature [17] are deposited in Supporting information.…”

“…Through the treatment of 5-allyl-2-hydroxy-3-methoxybenzaldehyde and 1,2-diaminobenzene at a molar ratio of 2:1 in absolute MeOH under refluxing, the condensation reaction and the subsequent cyclization reaction produced the off-white allylfunctionalized benzimidazole-based ligand HL in a comparable yield of 56% to the stepwise approach [17]. As shown in Scheme 1, further self-assembly of equimolar amounts of the ligand HL and…”

“…As a matter of fact, the solution can also resort to systems of f-f multinuclear emitters, where more efficient energy transfer is actually induced by the polymetallic electronic communications. Unfortunately, for the reported examples of either NIR luminescent Ln 4 (Salen) 4 -(Ln ¼ Nd, Yb or Er) [15,16] or green-light Tb 3 (Benzimidazole) 4 -grafted [17] polymers, the luminescent quenching [14] from OH-or OH À -vibrational oscillators directly around the three or four Ln 3þ ions, fatal to quantum efficiency, is not effectively avoided. Herein, based on the consideration of complete avoidance of oscillators around multiple Ln 3þ ions with electronic communications, each of allyl-containing while [Ln 3 (Benzimidazole) 4 ]-arrayed complex monomers {[Ln 3 (L) 4 (NO 3 ) 6 ]$(NO 3 )(H 3 O) 2 } (1e7) is copolymerized with NBE through a controllable ROMP, and PNBEassisted matrix is expected to make its new Ln 3 -grafted polymers toward desired physical properties including good Ln 3þ -centered luminescence.…”