A Novel Right-Angled Ligand that Forms Polymeric Metal−Organic Frameworks with Nanometer-Sized Square Cavities

Abstract

A new right angle-shaped ligand, 2,2′-bis(4-pyridyl)-9,9′-spirobifluorene (L), is designed and synthesized. Treatment of L with silver(I) ions leads to linear polymeric metal-organic frameworks, [Ag(L) 2 ] + (1), that feature square subunits. Single-crystal X-ray analysis reveals that [Ag(L) 2 ] + has a one-dimensional double-stranded polymeric chain comprising square grids with cavity dimensions of ca. 8 Å × 8 Å. By π-π stacking of adjacent double-stranded chains, the structure is extended into a two-dimensional (2D) layer framework with a unique quasiaperture (dimensions of ca. 14 Å × 8 Å). Each 2D layer is inclined and mutually interpenetrated, which gives rise to the three-dimensional interlocked network structure. Compound 1‚(BF 4 )(CH 3 OH) crystallizes in the monoclinic system, space group C2/c, with chemical formula C 71 H 49 N 4 OBF 4 Ag, a ) 25.709(1) Å, b ) 14.4164(6) Å, c ) 15.6865-(7) Å, β ) 109.220(2)°, and Z ) 4.

4-Pyridyl-9,9′-spirobifluorenes as Host Materials for Green and Sky-Blue Phosphorescent OLEDs

“…These angles are similar to those found (i) in its disubstituted analogue 2,2'-bis(4-Pyridyl)-9,9'-spirobifluorene (32.25° and 33.01°),33 (ii) in 2-Ph-SBF (37.4° in molecule 1)25 and (iii) in other 2-substituted SBFs 34. In the meantime, the distance between the two closest hydrogen atoms of the pyridyl ring (Ha and Hb) and of those of Ph4 (H1 and H3) is measured between 2.27 and 2.42 Å, that is lower or equal to the sum of van der Walls radii35 indicating some interactions between the hydrogens H1/Ha and H3/Hb.…”

“…Indeed, a dihedral angle as high as 16.8° between Ph3 and Ph4 mean planes is measured for 4-4Py-SBF, four times higher than the deformation found in the non 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 13 molecule 2 respectively), similar to that recorded for 2,2'-bis(4-Pyridyl)-9,9'-spirobifluorene (87.9°) 33 and for SBF (89.0°), 32 meaning that no significant deformation in the spiro-configuration is induced by the presence of the pyridine ring neither in C4, nor in C2.…”

“…In the meantime, the distance between the two closest hydrogen atoms of the pyridyl ring (Ha and Hb) and of those of Ph4 (H1 and H3) is measured between 2.27 and 2.42 Å, that is lower or equal to the sum of van der Walls radii35 indicating some interactions between the hydrogens H1/Ha and H3/Hb. This short distance is similar to the distances measured (i) in 2,2'-bis(4-Pyridyl)-9,9'-spirobifluorene (between 2.3 and 2.38 Å),33 (ii) in 2-Ph-SBF (between 2.36 and 2.39 Å in molecule 1)25 and (iii) in other 2-substituted SBFs 34. We note that in 4-substituted compounds, 4-4Py-SBF and 4-Ph-SBF, the H3-Ha distance is longer (from 2.44 to 2.68 Å) than in 2-substituted compounds indicating no interaction between H3/Ha contrary to what is observed for 2-Ph-SBF.…”

Structure–property relationship of 4-substituted-spirobifluorenes as hosts for phosphorescent organic light emitting diodes: an overview

“…6,7 From a more fundamental point of view, the orthogonal configuration induced by the spiro carbon also allows to design shape persistent molecules with specific arrangements, which in turn has peculiar electronic consequences. 3,4,[8][9][10][11][12][13][14][15] In addition, the application field of the SBF scaffold is not only restricted to electronics and SBF has also found many other appealing applications as chiral ligand, [16][17][18][19] electropolymerizable building block, [20][21][22][23][24][25][26] homogeneous 27 and heterogeneous 23-25, 28, 29 catalysts or as building unit in coordination polymers, [30][31][32] clearly showing the versatility of this fragment. Sixteen positions of substitutions are available on the SBF backbone, eight on each fluorene unit (figure 1).…”

Synthesis of 2,2′-diamino-7-tert-butyl-9,9′-spirobifluorene starting from 4,4′-di-tert-butylbiphenyl

“…Dinitrospirobifluorene can be reduced to the diamine by several pathways [4,16,21]. We chose an iron powder/HCl mixture for the reduction of the nitro group because of its easy availability, environmental safety, and low cost [22].…”