Facile Synthesis and Structures of Cyclic Triimidazole and Its Boric Acid Adduct

Abstract

Cyclic triimidazole, C9H6N6 (1), was prepared by thermolysis of the easily prepared copper imidazolate framework solid, Cu(C3H3N2)2 (2), providing a convenient route to this potentially useful tecton for molecular design. Anhydrous 1 and a hydrate, 1·0.5H2O, were characterized by single-crystal X-ray diffraction. Hydrate 1·0.5H2O contains two crystallographically independent 1 molecules. Supramolecular structures of 1 and 1·0.5H2O feature stacking arrangements in which the 1 molecule deviates from idealized geometry. A 3-fold H-bond acceptor 1 forms an adduct with boric acid, 1·B(OH)3, which was also structurally characterized. This adduct is composed of hydrogen-bonded sheets of 1 and B(OH)3 molecules with sheet interplanar separations of 3.175(4) Å and B(OH)3 boron atoms positioned above and below the centroids of 1 in adjacent sheets. Unlike 1 and its hydrate, 1·B(OH)3 contains 1 molecules that display crystallographically required D 3h symmetry. Anhydrous 1 crystallizes in the triclinic system, space group P1̅, with a = 7.2138(12), b = 8.3667(15), c = 8.8361(13) Å, α = 99.826(13), β = 113.825(10), γ = 110.721(11)°, V = 424.55(12) Å3, Z = 2; 1 2 ·H2O (or 1·0.5H2O), triclinic, P1̅, a = 7.5608(3), b = 7.5669(5), c = 15.8436(8) Å, α = 84.504(3), β = 81.269(3), γ = 87.038(3)°, V = 891.18(8) Å3, Z = 2; 1·B(OH)3, trigonal, P3̅, a = 10.1186(3), b = 10.1186(3), c = 6.3488(4) Å, α = 90, β = 90, γ = 120°, V = 562.94(4) Å3, Z = 2.

Extrinsic Heavy Metal Atom Effect on the Solid‐State Room Temperature Phosphorescence of Cyclic Triimidazole

“…The formula units comprise octahedral hexa‐aqua metal cations [M(H 2 O) 6 ] 2+ capped by the two symmetry‐related tetrahedral anions held in perching tripod positions via three OH(water)⋅⋅⋅Cl(F) hydrogen bonds, and two TT ligands attached to the metal cations via OH⋅⋅⋅N hydrogen bonds (Figure and Table S2 in SI). The Cd‐O distances are equal to 2.287(2) and 2.2857(19) Å in 2 , 3 , and Zn‐O distance is equal to 2.0973(17) Å in 4 , respectively in agreement with literature data …”

“…On the other side, its crystals show a strong, broad, featureless emission centered at 400 nm ( Φ =30 %, λ exc =350 nm) which is the result of the superimposition of a prompt (λ em =400 nm, τ in the nanosecond regime) and a longer wavelength (λ em =525 nm) RTUP which lasts for about 3.6 s (τ av =970 ms) and is affected by the degree of crystallinity but is inert to oxygen. Single crystal XRD analysis revealed that the molecules are slightly twisted with respect to an idealized C 3 h symmetry and stack in face‐to‐face antiparallel packed zigzag columns with distances between centroids of the central rings equal to 3.73 and 3.95 Å (Figure , left) . Such short distances are indicative of strong π–π interactions in the ground state, associated with a large interchromophoric π‐stacking area and formation of H‐aggregates which are responsible for the CIE behavior and are at the basis of the RTUP …”

“…Single crystal XRD analysis revealed that the molecules are slightly twisted with respect to an idealized C 3h symmetry and stack in face-to-face antiparallel packedz igzag columns with distances between centroids of the central rings equal to 3.73 and 3.95 (Figure 1, left). [10] Such short distances are indicative of strong p-p interactions in the ground state, associated with al arge interchromophoric p-stacking area andf ormation of H-aggregates which are responsible for the CIE behavior and are at the basis of the RTUP. [4] Aimed at verifying the effect of am etal on TT photoluminescence we have synthetized as eries of metal containing derivatives.…”

“…The Cd-O distances are equal to 2.287(2) and 2.2857(19) in 2, 3,a nd Zn-O distance is equal to 2.0973(17) in 4,respectively in agreement with literature data. [10] In accordance with the three-fold inversion axis symmetry, each inorganic cation arranges around six TT ligands in two parallel planes (Figure6)h eld via OH···N hydrogen bonds, while each anion arranges four TT ligandsi nt wo parallel planes, three held with the anion via CH···O(F)h ydrogen bonds (Table S2), and one held with the anion via anion-p interactions (the distances between F/O and the centroids of the central rings are equal to 2.629 for 2, 2.669 for 3 and 2.644 for 4). Thus, each TT chromophore is surroundedb yt hree cations and three anionst hat exclude the homomeric TT side contacts.…”

“…All reagents were purchased from chemical suppliers and used without further purification unless otherwise stated. Triimidazo[1,2‐ a :1′,2′‐ c :1′′,2′′‐ e ][1,3,5]triazine ( TT ) was prepared according to literature procedures . Steady state emission and excitation spectra and photoluminescence lifetimes were obtained using a FLS 980 (Edinburg Instrument Ltd) and a Nanolog (Horiba Scientific) spectrofluorimeter.…”