Syntheses and comprehensive characterization of two closely related series of isomorphous metal-organic frameworks (MOFs) based on triazolyl isophthalate linkers with the general formula ∞(3)[M2(R(1)-R(2)-trz-ia)2] (M = Cu, Zn) are presented. Using solvothermal synthesis and synthesis of microcrystalline materials on the gram scale by refluxing a solution of the starting materials, 11 MOFs are readily available for a systematic investigation of structure-property relationships. The networks of the two series are assigned to rutile (rtl) (1-4) and α-PbO2 (apo) (5-9) topology, respectively. Due to the orientation of the triazole substituents toward the cavities, both the pore volume and the pore diameter can be adjusted by choice of the alkyl substituents. Compounds 1-9 exhibit pronounced microporosity with calculated porosities of 31-53% and show thermal stability up to 390 °C as confirmed by simultaneous thermal analysis. Systematic investigation of adsorption properties by CO2 (298 K) and N2 (77 K) adsorption studies reveal remarkable network flexibility induced by alkyl substituents on the linker. Fine-tuning of the gate opening pressure and of the hysteresis shape is possible by adjusting the substitution pattern and by choice of the metal ion.

The coordination behavior of the neutral calix[4]arene-based ligand L exhibiting dangling phosphonate ester and picolinamide groups in 1,3-and 2,4-distal positions towards a series of lanthanide ions was examined. Reaction of L with Ln(NO 3 ) 3 in MeOH afforded mononuclear [LnL(μ 1,3 -NO 3 ) 2 ]NO 3 complexes [Ln = La (6), Pr (7), Eu (8), Gd (9)]. X-ray crystallography for 6 and 7 revealed tenfold coordination by phosphoryl O, amide O, and pyridine N atoms from L and four O atoms from two chelating nitrato coligands. Treatment of the [LnL(μ 1,3 -NO 3 ) 2 ]NO 3 salts with NaBPh 4 leads to metathesis of the counterion and, in the case of Pr, Eu, and Gd, to substitution of one nitrato coligand by a methanol molecule yielding [LnL(μ 1,3 -NO 3 ) 2-n (MeOH) n ](BPh 4 ) n+1 for n = 0, Ln = La (10) and [a] 3113 Scheme 3. Synthesis of lanthanide complexes 10-13 by nitrate metathesis.

This work presents the syntheses and comprehensive characterization of six paddlewheel based metal− organic frameworks (MOFs) with the general formula ∞ 3 [M 2 L 2 ] (M = Cu, Co, Zn; L = bis(carboxyphenyl)-1,2,4-triazole) forming an isoreticular series with rutile (rtl) topology. These microporous materials are suitable for a systematic investigation of structure−property relationships based on the impact of the metal ion. Depending on the metal ion, the calculated porosities and the pore diameters reach from 58% to 61% and 300 to 750 pm, respectively. Simultaneous thermal analysis and temperature dependent PXRD studies reveal varying thermal behavior with stabilities up to 400°C. In the case of syntheses with various Co 2+ /Cu 2+ , Co 2+ /Zn 2+ , and Cu 2+ /Zn 2+ ratios, ICP-OES analyses and SEM-EDX studies confirm the formation of mixed metal MOFs and the metal ion distribution in the bulk samples as well as within the crystals. For the systematic investigation of CO 2 (298 K) and N 2 (77 K) adsorption properties, all materials were previously subjected to extraction with supercritical CO 2 . Depending on the metal ion, this procedure causes different phase transitions for each compound. As a result, adsorption studies reveal varying network flexibility for these MOFs. This study is one of the rare examples demonstrating that targeted modification of gate opening pressure, hysteresis shape, and adsorbed amounts of CO 2 or N 2 are possible by choice of the metal ion. This finding is supported by adsorption studies on the mixed metal MOF ∞ 3 [(Cu 0.48 Co 0.52 ) 2 (p-L) 2 )], showing CO 2 adsorption/desorption characteristics of both homonuclear copper and cobalt materials, whereas N 2 does not induce gate opening of the framework, as observed for the cobalt MOF. Furthermore, catalytic studies reveal that ∞ 3 [Cu 2 (p-L) 2 )] is a suitable catalyst for the oxidation of cyclohexene with tert-butylhydroperoxide (TBHP) with high conversion of the starting materials and good selectivity. Its robustness under the applied catalysis conditions leads to similar conversions in repetition measurements.

The dinuclear Ni(II) complex [Ni2(L(2))][ClO4]2 (3) supported by the 28-membered hexaaza-dithiophenolate macrocycle (L(2))(2-) binds the N3(-) ion specifically end-on yielding [Ni2(L(2))(μ(1,1)-N3)][ClO4] (7) or [Ni2(L(2))(μ(1,1)-N3)][BPh4] (8), while the previously reported complex [Ni2L(1)(μ(1,3)-N3)][ClO4] (2) of the 24-membered macrocycle (L(1))(2-) coordinates it in the end-to-end fashion. A comparison of the X-ray structures of 2, 3, and 7 reveals the form-selective binding of complex 3 to be a consequence of its preorganized, channel-like binding pocket, which accommodates the azide anion via repulsive CH···π interactions in the end-on mode. In contrast to [Ni2L(1)(μ(1,3)-N3)][ClO4] (2), which features a S = 0 ground state, [Ni2(L(2))(μ(1,1)-N3)][BPh4] (8) has a S = 2 ground state that is attained by competing antiferromagnetic and ferromagnetic exchange interactions via the thiolato and azido bridges with a value for the magnetic exchange coupling constant J of 13 cm(-1) (H = -2JS1S2). These results are further substantiated by density functional theory calculations. The stability of the azido-bridged complex determined by isothermal titration calorimetry in MeCN/MeOH 1/1 v/v (log K11 = 4.88(4) at I = 0.1 M) lies in between those of the fluorido- (log K11 = 6.84(7)) and chlorido-bridged complexes (log K11 = 3.52(5)). These values were found to compare favorably well with the equilibrium constants derived at lower ionic strength (I = 0.01 M) by absorption spectrophotometry (log K11 = 5.20(1), 7.77(9), and 4.13(3) for N3(-), F(-), and Cl(-) respectively).