Supramolecular Interactions Direct the Formation of Two Structural Polymorphs from One Building Unit in a One-Pot Synthesis

Construction and structural transformation of two coordination sphere supramolecular isomers based on Co(ii) and 4-(2-pyridyl)-NH-1,2,3-triazole via one-pot synthesis

Two coordination sphere supramolecular isomers based on Co(ii) have been obtained via one-pot synthesis. The structural transformation process has been investigated with the help of mass spectroscopy and theoretical calculations.

In Situ Metal-Assisted Ligand Modification Induces Mn4 Cluster-to-Cluster Transformation: A Crystallography, Mass Spectrometry, and DFT Study

Dehydration of (S,S)-1,2-bis(1H-benzo[d]imidazol-2-yl)ethane-1,2-diol (H₄ L) to (Z)-1,2-bis(1H-benzo[d]imidazol-2-yl)ethenol) (H₃ L') was found to be metal-assisted, occurs under solvothermal conditions (H₂ O/CH₃ OH), and leads to [Mn^II ₄ (H₃ L)₄ Cl₂ ]Cl₂ ⋅5 H₂ O⋅5 CH₃ OH (Mn₄ L₄ ) and [Mn^II ₄ (H₂ L')₆ (μ₃ -OH)]Cl⋅4 CH₃ OH⋅H₂ O (Mn₄ L'₆ ), respectively. Their structures were determined by single-crystal XRD. Extensive ESI-MS studies on solutions and solids of the reaction led to the proposal consisting of an initial stepwise assembly of Mn₄ L₄ from the reactants via [MnL] and [Mn₂ L₂ ] below 80 °C, and then disassembly to [MnL] and [MnL₂ ] followed by ligand modification before reassembly to Mn₄ L'₆ via [MnL'], [MnL'₂ ], and [Mn₂ L'₃ ] with increasing solvothermal temperature up to 140 °C. Identification of intermediates [Mn₄ L_x L'_6-x ] (x=5, 4, 3, 2, 1) in the process further suggested an assembly/disassembly/in situ reaction/reassembly transformation mechanism. These results not only reveal that multiple phase transformations are possible even though they were not realized in the crystalline state, but also help to better understand the complex transformation process between coordination clusters during "black-box" reactions.

Tuning Semiconductor Performance of Nickel Complexes through Crystal Transformation

Crystal transformation between two polymorphs (green, 1-G, and red, 1-R) of the square-planar nickel complex NiL₂ (L = 2-ethoxy-6-( N-methyliminomethyl)phenolate) and their tuning effect to semiconductor properties were studied both experimentally and theoretically. When 1-G is heated to 413 K, it converts to 1-R, whereas soaking 1-R in several kinds of solvents causes it to revert to 1-G. Crystallographic and PXRD studies reveal the dramatic changes in crystal dimensions due to the changes of packing models. Heating device made from 1-G (D-1-G(298)) at 413 K significantly increases the electrical conductivity from 6.55 × 10^-4 S cm^-1 for D-1-G(298) to 1.11 × 10^-3 S cm^-1 for D-1-G(413), showing significant crystal form dependence. Heat-treating D-1-G and D-1-R devices at different temperatures clearly reveals the reason for the conductivity tuning. Thus, the conductivity of NiL₂-based devices could be well tuned through crystal transformation by heating or by soaking in solvent. Theoretical calculations clearly revealed the reason for such conductivity changes and also predicted that both polymorphs are good p-type semiconductors with hole mobilities of 1.63 × 10^-2 (1-G) and 2.11 × 10^-1 cm² V^-1 s^-1 (1-R).

Ferromagnetic coupling in copper benzimidazole chloride: structural, mass spectrometry, magnetism, and DFT studies

The square planar Cu(Hmbm)Cl₂ form pseudo-hexagonal magnetic layers with ferromagnetic couplings of J(Cu–Cl2a⋯Cu1) = +0.99(30) cm⁻¹, J′(π⋯π) = +0.35(16) cm⁻¹, and g = 2.38(2).