Hydrothermal Synthesis and Structure of Coordination Polymers by Combination of Bipyrazole and Aromatic Dicarboxylate Ligands

Nine new coordination polymers, namely 2∞[Ag(Hp2CA)(Me4bpz)] (I), 3∞[Zn2(p2CA)2(Me4bpz)] (II), 2∞[Cd(OAc)2(Me4bpz)(H2O)] (III), 1∞[Ag2(m2CA)(Me4bpz)2] (IV), 3∞[Zn(m2CA)(Me4bpz)] (V), 2∞[Cd(m2CA)(Me4bpz)]·H2O (VI), 1∞[Ag(OAc)(Me4bpz)2]·5.4 H2O (VII), 3∞[Zn2(OHm2CA)2(Me4bpz)2]·1.75 H2O (VIII), and 2∞[Cd(OHm2CA)(Me4bpz)(H2O)] (IX) [Hp2CA, terephthalic acid monoanion; p2CA, terephthalic acid dianion; OAc, acetate; m2CA, isophthalic acid dianion; OHm2CA, 5-hydroxy-isophthalic acid dianion; Me4bpz, 3,3′,5,5′-tetramethyl-4,4′-bipyrazole], were obtained from acetate hydrates of Ag+, Zn2+, and Cd2+ and mixed ligand systems consisting of Me4bpz and the respective aromatic dicarboxylic acid by means of hydrothermal synthesis. The compounds were characterized by means of X-ray single-crystal structure analysis, elemental analysis, and IR spectroscopy. The topologies realized in these coordination polymers vary from simple one-dimensional polymers to complex three-dimensional frameworks. Hydrogen bonds of different types with influence on the resulting structures are observed in all compounds

Hydrothermal Synthesis and Structure of Coordination Polymers by Combination of Bipyrazole and Aromatic Dicarboxylate Ligands

Nine new coordination polymers, namely 2∞[Ag(Hp2CA)(Me4bpz)] (I), 3∞[Zn2(p2CA)2(Me4bpz)] (II), 2∞[Cd(OAc)2(Me4bpz)(H2O)] (III), 1∞[Ag2(m2CA)(Me4bpz)2] (IV), 3∞[Zn(m2CA)(Me4bpz)] (V), 2∞[Cd(m2CA)(Me4bpz)]·H2O (VI), 1∞[Ag(OAc)(Me4bpz)2]·5.4 H2O (VII), 3∞[Zn2(OHm2CA)2(Me4bpz)2]·1.75 H2O (VIII), and 2∞[Cd(OHm2CA)(Me4bpz)(H2O)] (IX) [Hp2CA, terephthalic acid monoanion; p2CA, terephthalic acid dianion; OAc, acetate; m2CA, isophthalic acid dianion; OHm2CA, 5-hydroxy-isophthalic acid dianion; Me4bpz, 3,3′,5,5′-tetramethyl-4,4′-bipyrazole], were obtained from acetate hydrates of Ag+, Zn2+, and Cd2+ and mixed ligand systems consisting of Me4bpz and the respective aromatic dicarboxylic acid by means of hydrothermal synthesis. The compounds were characterized by means of X-ray single-crystal structure analysis, elemental analysis, and IR spectroscopy. The topologies realized in these coordination polymers vary from simple one-dimensional polymers to complex three-dimensional frameworks. Hydrogen bonds of different types with influence on the resulting structures are observed in all compounds

Adsorption Structures of Water in NaX Studied by DRIFT Spectroscopy and Neutron Powder Diffraction

Diffuse reflectance infrared Fourier transform spectroscopic (DRIFTS) measurements (4000−1500 cm-1) and the results of neutron powder diffraction have been combined to study the structure of adsorption complexes of water in a NaX zeolite at different water loadings (25, 48, 72, and 120 water molecules per unit cell, respectively). Sharp bands corresponding to non-hydrogen-bonded OH groups of water molecules and broad associate bands due to hydrogen-bonded molecules are observed in the DRIFT spectra. We observe a remarkable downshift of the high-frequency associate band in a narrow temperature interval when the water amount decreases from 120 to 72 molecules per unit cell, which could signify some kind of “phase transition” for the water inside the zeolite cavities. Neutron powder diffraction results show that water molecules are predominantly localized in or near the 12-ring windows. Water molecules with hydrogen-bonded and non-hydrogen-bonded OH groups were found, in agreement with the observation of sharp and broad bands in the DRIFT spectra. We find strong evidence for the formation of cyclic hexamers of water molecules localized in the 12-ring windows, which are further stabilized by hydrogen bonds to framework oxygen atoms

Adsorption Structures of Water in NaX Studied by DRIFT Spectroscopy and Neutron Powder Diffraction

Diffuse reflectance infrared Fourier transform spectroscopic (DRIFTS) measurements (4000−1500 cm-1) and the results of neutron powder diffraction have been combined to study the structure of adsorption complexes of water in a NaX zeolite at different water loadings (25, 48, 72, and 120 water molecules per unit cell, respectively). Sharp bands corresponding to non-hydrogen-bonded OH groups of water molecules and broad associate bands due to hydrogen-bonded molecules are observed in the DRIFT spectra. We observe a remarkable downshift of the high-frequency associate band in a narrow temperature interval when the water amount decreases from 120 to 72 molecules per unit cell, which could signify some kind of “phase transition” for the water inside the zeolite cavities. Neutron powder diffraction results show that water molecules are predominantly localized in or near the 12-ring windows. Water molecules with hydrogen-bonded and non-hydrogen-bonded OH groups were found, in agreement with the observation of sharp and broad bands in the DRIFT spectra. We find strong evidence for the formation of cyclic hexamers of water molecules localized in the 12-ring windows, which are further stabilized by hydrogen bonds to framework oxygen atoms

Adsorption Structures of Water in NaX Studied by DRIFT Spectroscopy and Neutron Powder Diffraction

Diffuse reflectance infrared Fourier transform spectroscopic (DRIFTS) measurements (4000−1500 cm-1) and the results of neutron powder diffraction have been combined to study the structure of adsorption complexes of water in a NaX zeolite at different water loadings (25, 48, 72, and 120 water molecules per unit cell, respectively). Sharp bands corresponding to non-hydrogen-bonded OH groups of water molecules and broad associate bands due to hydrogen-bonded molecules are observed in the DRIFT spectra. We observe a remarkable downshift of the high-frequency associate band in a narrow temperature interval when the water amount decreases from 120 to 72 molecules per unit cell, which could signify some kind of “phase transition” for the water inside the zeolite cavities. Neutron powder diffraction results show that water molecules are predominantly localized in or near the 12-ring windows. Water molecules with hydrogen-bonded and non-hydrogen-bonded OH groups were found, in agreement with the observation of sharp and broad bands in the DRIFT spectra. We find strong evidence for the formation of cyclic hexamers of water molecules localized in the 12-ring windows, which are further stabilized by hydrogen bonds to framework oxygen atoms

Adsorption Structures of Water in NaX Studied by DRIFT Spectroscopy and Neutron Powder Diffraction

Diffuse reflectance infrared Fourier transform spectroscopic (DRIFTS) measurements (4000−1500 cm-1) and the results of neutron powder diffraction have been combined to study the structure of adsorption complexes of water in a NaX zeolite at different water loadings (25, 48, 72, and 120 water molecules per unit cell, respectively). Sharp bands corresponding to non-hydrogen-bonded OH groups of water molecules and broad associate bands due to hydrogen-bonded molecules are observed in the DRIFT spectra. We observe a remarkable downshift of the high-frequency associate band in a narrow temperature interval when the water amount decreases from 120 to 72 molecules per unit cell, which could signify some kind of “phase transition” for the water inside the zeolite cavities. Neutron powder diffraction results show that water molecules are predominantly localized in or near the 12-ring windows. Water molecules with hydrogen-bonded and non-hydrogen-bonded OH groups were found, in agreement with the observation of sharp and broad bands in the DRIFT spectra. We find strong evidence for the formation of cyclic hexamers of water molecules localized in the 12-ring windows, which are further stabilized by hydrogen bonds to framework oxygen atoms

Adsorption Structures of Water in NaX Studied by DRIFT Spectroscopy and Neutron Powder Diffraction

Diffuse reflectance infrared Fourier transform spectroscopic (DRIFTS) measurements (4000−1500 cm-1) and the results of neutron powder diffraction have been combined to study the structure of adsorption complexes of water in a NaX zeolite at different water loadings (25, 48, 72, and 120 water molecules per unit cell, respectively). Sharp bands corresponding to non-hydrogen-bonded OH groups of water molecules and broad associate bands due to hydrogen-bonded molecules are observed in the DRIFT spectra. We observe a remarkable downshift of the high-frequency associate band in a narrow temperature interval when the water amount decreases from 120 to 72 molecules per unit cell, which could signify some kind of “phase transition” for the water inside the zeolite cavities. Neutron powder diffraction results show that water molecules are predominantly localized in or near the 12-ring windows. Water molecules with hydrogen-bonded and non-hydrogen-bonded OH groups were found, in agreement with the observation of sharp and broad bands in the DRIFT spectra. We find strong evidence for the formation of cyclic hexamers of water molecules localized in the 12-ring windows, which are further stabilized by hydrogen bonds to framework oxygen atoms

Synthesis of NBN-Type Zigzag-Edged Polycyclic Aromatic Hydrocarbons: 1,9-Diaza-9a-boraphenalene as a Structural Motif

A novel class of dibenzo-fused 1,9-diaza-9a-boraphenalenes featuring zigzag edges with a nitrogen–boron–nitrogen bonding pattern named NBN-dibenzophenalenes (NBN-DBPs) has been synthesized. Alternating nitrogen and boron atoms impart high chemical stability to these zigzag-edged polycyclic aromatic hydrocarbons (PAHs), and this motif even allows for postsynthetic modifications, as demonstrated here through electrophilic bromination and subsequent palladium-catalyzed cross-coupling reactions. Upon oxidation, as a typical example, NBN-DBP 5a was nearly quantitatively converted to σ-dimer 5a-2 through an open-shell intermediate, as indicated by UV–vis–NIR absorption spectroscopy and electron paramagnetic resonance spectroscopy corroborated by spectroscopic calculations, as well as 2D NMR spectra analyses. In situ spectroelectrochemistry was used to confirm the formation process of the dimer radical cation 5a-2•+. Finally, the developed new synthetic strategy could also be applied to obtain π-extended NBN-dibenzoheptazethrene (NBN-DBHZ), representing an efficient pathway toward NBN-doped zigzag-edged graphene nanoribbons

Synthesis of NBN-Type Zigzag-Edged Polycyclic Aromatic Hydrocarbons: 1,9-Diaza-9a-boraphenalene as a Structural Motif

A novel class of dibenzo-fused 1,9-diaza-9a-boraphenalenes featuring zigzag edges with a nitrogen–boron–nitrogen bonding pattern named NBN-dibenzophenalenes (NBN-DBPs) has been synthesized. Alternating nitrogen and boron atoms impart high chemical stability to these zigzag-edged polycyclic aromatic hydrocarbons (PAHs), and this motif even allows for postsynthetic modifications, as demonstrated here through electrophilic bromination and subsequent palladium-catalyzed cross-coupling reactions. Upon oxidation, as a typical example, NBN-DBP <b>5a</b> was nearly quantitatively converted to σ-dimer <b>5a-2</b> through an open-shell intermediate, as indicated by UV–vis–NIR absorption spectroscopy and electron paramagnetic resonance spectroscopy corroborated by spectroscopic calculations, as well as 2D NMR spectra analyses. In situ spectroelectrochemistry was used to confirm the formation process of the dimer radical cation <b>5a-2</b>^•+. Finally, the developed new synthetic strategy could also be applied to obtain π-extended NBN-dibenzoheptazethrene (NBN-DBHZ), representing an efficient pathway toward NBN-doped zigzag-edged graphene nanoribbons

Synthesis of NBN-Type Zigzag-Edged Polycyclic Aromatic Hydrocarbons: 1,9-Diaza-9a-boraphenalene as a Structural Motif

A novel class of dibenzo-fused 1,9-diaza-9a-boraphenalenes featuring zigzag edges with a nitrogen–boron–nitrogen bonding pattern named NBN-dibenzophenalenes (NBN-DBPs) has been synthesized. Alternating nitrogen and boron atoms impart high chemical stability to these zigzag-edged polycyclic aromatic hydrocarbons (PAHs), and this motif even allows for postsynthetic modifications, as demonstrated here through electrophilic bromination and subsequent palladium-catalyzed cross-coupling reactions. Upon oxidation, as a typical example, NBN-DBP 5a was nearly quantitatively converted to σ-dimer 5a-2 through an open-shell intermediate, as indicated by UV–vis–NIR absorption spectroscopy and electron paramagnetic resonance spectroscopy corroborated by spectroscopic calculations, as well as 2D NMR spectra analyses. In situ spectroelectrochemistry was used to confirm the formation process of the dimer radical cation 5a-2•+. Finally, the developed new synthetic strategy could also be applied to obtain π-extended NBN-dibenzoheptazethrene (NBN-DBHZ), representing an efficient pathway toward NBN-doped zigzag-edged graphene nanoribbons