Elongated and substituted triazine-based tricarboxylic acid linkers for MOFs

Abstract

New triazine-based tricarboxylic acid linkers were prepared as elongated relatives of triazinetribenzoic acid (TATB). Additionally, functional groups (NO2, NH2, OMe, OH) were introduced for potential post-synthetic modification (PSM) of MOFs. Functionalized tris(4-bromoaryl)triazine “cores” (3a,3b) were obtained by unsymmetric trimerization mixing one equivalent of an acid chloride (OMe or NO2 substituted) with two equivalents of an unsubstituted nitrile. Triple Suzuki coupling of the cores 3 with suitable phenyl- and biphenylboronic acid derivatives provided elongated tricarboxylic acid linkers as carboxylic acids 17 and 20 or their esters 16 and 19. Reduction of the nitro group and cleavage of the methoxy group gave the respective amino and hydroxy-substituted triazine linkers.

Substituted 1,3,5-Triazine Hexacarboxylates as Potential Linkers for MOFs

“…using for instance TATB (1,3,5,-triazine-2,4,6-tribenzoate) instead of BTB (1,3,5-benzenetribenzoate), see above and ref. [12,13] - is the more pronounced planarity of the aromatic rings in the triaryltriazine system. However, in the hexadentate linkers 6 and 7 , biphenyl substructures have been generated by the cross-coupling reaction.…”

“…Under nitrogen, a mixture of 2-(4-bromo-3-nitrophenyl)-4,6-bis(4-bromophenyl)-1,3,5-triazine ( 3b , 100 mg, 170 µmol) [13], dimethyl 5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-isophthalate ( 4 , 245 mg, 765 µmol), tetrakis(triphenylphosphine)-palladium(0) (30 mg, 26 µmol), and potassium phosphate (234 mg, 1.10 mmol) in a mixture of 1,4-dioxane (10 mL) and deionized water (1 mL) was heated to reflux for 48 h. After evaporation of the dioxane in vacuo, the residue was dissolved in water (25 mL) and extracted with chloroform (3 × 25 mL). The combined organic layer was washed with brine (25 mL), dried with magnesium sulfate, and filtered.…”

“…Under nitrogen, 2-(4-bromo-3-methoxyphenyl)-4,6-bis(4-bromophenyl)-1,3,5-triazine ( 3c , 100 mg, 175 µmol) [13], dimethyl 5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-isophthalate ( 4 , 252 mg, 788 µmol) and potassium phosphate (234 mg, 1.10 mmol) were mixed with a mixture of 1,4-dioxane (10 mL), and deionized water (1 mL). Tetrakis(triphenylphosphine)-palladium(0) (30 mg, 26 µmol) was added, and the mixture was stirred for 48 h at 100 °C.…”

“…In this work, we describe the syntheses of mono-functionalized hexadentate ligands. In contrast to the linkers used in NU-109 and NU-110, we have chosen a 1,3,5-triazine as the central aromatic ring because triaryltriazines are more planar than triarylbenzenes [12,13]. A variety of related tridentate and monofunctionalized triazine linkers 1 and 2 have been synthesized (see Figure 1) [14].…”

“…A variety of related tridentate and monofunctionalized triazine linkers 1 and 2 have been synthesized (see Figure 1) [14]. Some of them have already been used in the syntheses of MOFs, yielding PCN-6 analogues that contain additional functionalities such as NO 2 and NH 2 [13,14,15,16].…”