Synthesis, crystal structures and luminescent properties of two one-dimensional cadmium(II) coordination polymers generated from polydentate Schiff-base ligand

Cu(ii)-induced twisting of the biphenyl core: exploring the effect of structure and coordination environment of biphenyl-based chiral copper(ii) complexes on interaction with calf-thymus DNA

Biphenyl core-based clip-like receptors get twisted after complexation with Cu²⁺. The extent of interaction of the optically active complexes with ct-DNA varies depending on the structure and coordination environment.

The Good, the Bad, and the Ugly: "HiPen", a New Dataset for Validating (S)QM/MM Free Energy Simulations

Indirect (S)QM/MM free energy simulations (FES) are vital to efficiently incorporating sufficient sampling and accurate (QM) energetic evaluations when estimating free energies of practical/experimental interest. Connecting between levels of theory, i.e., calculating Δ A l o w → h i g h , remains to be the most challenging step within an indirect FES protocol. To improve calculations of Δ A l o w → h i g h , we must: (1) compare the performance of all FES methods currently available; and (2) compile and maintain datasets of Δ A l o w → h i g h calculated for a wide-variety of molecules so that future practitioners may replicate or improve upon the current state-of-the-art. Towards these two aims, we introduce a new dataset, "HiPen", which tabulates Δ A g a s M M → 3 o b (the free energy associated with switching from an M M to an S C C - D F T B molecular description using the 3ob parameter set in gas phase), calculated for 22 drug-like small molecules. We compare the calculation of this value using free energy perturbation, Bennett's acceptance ratio, Jarzynski's equation, and Crooks' equation. We also predict the reliability of each calculated Δ A g a s M M → 3 o b by evaluating several convergence criteria including sample size hysteresis, overlap statistics, and bias metric ( Π ). Within the total dataset, three distinct categories of molecules emerge: the "good" molecules, for which we can obtain converged Δ A g a s M M → 3 o b using Jarzynski's equation; "bad" molecules which require Crooks' equation to obtain a converged Δ A g a s M M → 3 o b ; and "ugly" molecules for which we cannot obtain reliably converged Δ A g a s M M → 3 o b with either Jarzynski's or Crooks' equations. We discuss, in depth, results from several example molecules in each of these categories and describe how dihedral discrepancies between levels of theory cause convergence failures even for these gas phase free energy simulations.

Synthesis, crystal structures, luminescence properties of two metal coordination polymers derived from 5-substituted isophthalate and flexible bis (triazole) ligands

Two new metal complexes, [Ni(btx)(nip)(H2O)]n (1), {[Cd(btx)(mip)(H2O)]·H2O}n (2) (btx=1,4-bis(1,2,4-triazol-1-ylmethyl)benzene, H2nip=5-nitroisophthalic acid, H2mip=5-methyisophthalic acid) were synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction methods, IR spectroscopy, TGA and elemental analysis. Complex 1 features a 3D metal-organic framework with three-fold interpenetrating CdSO4-type topology. Complex 2 exhibits a 2D network with square grid units, which is further extended into a rare 3,5T1 three-dimensional supramolecular network via three modes of classical OH⋯O hydrogen bonds. In addition, luminescence properties of 1 and 2 have also been investigated in the solid state.

Structural versatility and luminescent properties in d(10) metal ion polymers with 1,4-naphthalenedicarboxylate acid and 4,4'-dipyridyl N,N'-dioxide

Hydrothermal reactions of d(10) metal ions (Cd(2+) and Zn(2+)) with 1,4-naphthalenedicarboxylate acid (1,4-H2NDC) and 4,4'-dipyridyl N,N'-dioxide (4,4'-dpdo) form two three-dimensional grid-like coordination polymers [Cd2(1,4-NDC)2(4,4'-dpdo)]·H2O 1 and [Zn4(μ3-OH)2(1,4-NDC)3(H2O)2](4,4'-dpdo)·2H2O 2. Both coordination polymers were characterized by single crystal X-ray diffraction, IR spectroscopy, XRPD, thermogravimetric and elemental analyses. Polymer 1 exhibits rare alternating arranged 1,4-NDC(2)(-) and 4,4'-dpdo spacers between adjacent 1D zigzag chains containing Cd-octahedral coordination geometries. Polymer 2 is constructed from infrequent chair-like [Zn4(μ3-OH)2](6+) inorganic SBUs with four- and six-coordination geometries and only 1,4-NDC(2)(-) as "single-bridge" and "double-bridges" to form a 3D framework. Both polymers give strong luminescent emissions in the solid state at room temperature.