Iodine(I) and Silver(I) Complexes of Benzoimidazole and Pyridylcarbazole Derivatives

The synthesis of iodine(I) complexes with either benzoimidazole or carbazole-derived sp 2 N -containing Lewis bases is described, as well as their corresponding silver(I) complexes. The addition of elemental iodine to the linear two-coordinate Ag(I) complexes produces iodine(I) complexes with a three-center four-electron (3c-4e) [N — I — N] + bond. The 1 H and 1 H- 15 N HMBC NMR studies unambiguously confirm the formation of the complexes in all cases via the [N — Ag — N] + → [N — I — N] + cation exchange, with the 15 N NMR chemical shift change between 94 to 111 ppm when compared to the free ligand. The single crystal X-ray crystallographic studies on four I + complexes revealed highly symmetrical [N — I — N] + bonds with I — N bond distances of 2.21 - 2.26 Å and N — I — N angles of 177 - 180 ° , whilst some of the corresponding Ag + complexes showed a clear deviation from linearity with N — Ag — N angles of ca. 150 ° and Ag — N bond distances of 2.09 - 2.18 Å.peerReviewe

Iodine(I) and Silver(I) Complexes of Benzoimidazole and Pyridylcarbazole Derivatives

The synthesis of iodine(I) complexes with either benzoimidazole or carbazole-derived sp 2 N -containing Lewis bases is described, as well as their corresponding silver(I) complexes. The addition of elemental iodine to the linear two-coordinate Ag(I) complexes produces iodine(I) complexes with a three-center four-electron (3c-4e) [N — I — N] + bond. The 1 H and 1 H- 15 N HMBC NMR studies unambiguously confirm the formation of the complexes in all cases via the [N — Ag — N] + → [N — I — N] + cation exchange, with the 15 N NMR chemical shift change between 94 to 111 ppm when compared to the free ligand. The single crystal X-ray crystallographic studies on four I + complexes revealed highly symmetrical [N — I — N] + bonds with I — N bond distances of 2.21 - 2.26 Å and N — I — N angles of 177 - 180 ° , whilst some of the corresponding Ag + complexes showed a clear deviation from linearity with N — Ag — N angles of ca. 150 ° and Ag — N bond distances of 2.09 - 2.18 Å.peerReviewe

Halogen-Bonded [N–I–N]− Complexes with Symmetric or Asymmetric Three-Center–Four-Electron Bonds

A series of LH[Z–I–Z] halogen(I) complexes, where Z = saccharinato or phthalimido anions and LH = pyridinium, pyrazinium, tetrabutyl (TBA)- or tetramethylammonium (TMA) cations, were prepared, structurally characterized, and discussed as complexes consisting of a [N–I–N]− anion with a three-center–four-electron (3c-4e) halogen bond, and a hydrogen-bonding (pyridinium or pyrazinium) or inert (TBA or TMA) cation. The symmetric [N–I–N]− anion, reminiscent of the triiodide [I–I–I]− anion, is found to be structurally equivalent to its cationic analogue [N–I–N]+ with N–I bond lengths of 2.26 Å. In contrast to the homoleptic [N–I–N]+ complexes, asymmetry of the N–I bond lengths (2.21 and 2.28 Å) was observed for those [N–I–N]− complexes which manifested a hydrogen bond to only one saccharinato moiety, thus being structurally analogous to the asymmetric heteroleptic [N–I–N]+ complexes. The results show that the 3c-4e [N–I–N] halogen bond, being either positively or negatively charged, can be asymmetrized by an external hydrogen bond ([N–I–N]−) or by using two different ligands (heteroleptic [N–I–N]+).peerReviewe

Supersaturated calcium carbonate solutions are classical.

Mechanisms of CaCO3 nucleation from solutions that depend on multistage pathways and the existence of species far more complex than simple ions or ion pairs have recently been proposed. Herein, we provide a tightly coupled theoretical and experimental study on the pathways that precede the initial stages of CaCO3 nucleation. Starting from molecular simulations, we succeed in correctly predicting bulk thermodynamic quantities and experimental data, including equilibrium constants, titration curves, and detailed x-ray absorption spectra taken from the supersaturated CaCO3 solutions. The picture that emerges is in complete agreement with classical views of cluster populations in which ions and ion pairs dominate, with the concomitant free energy landscapes following classical nucleation theory

Supersaturated calcium carbonate solutions are classical.

Mechanisms of CaCO3 nucleation from solutions that depend on multistage pathways and the existence of species far more complex than simple ions or ion pairs have recently been proposed. Herein, we provide a tightly coupled theoretical and experimental study on the pathways that precede the initial stages of CaCO3 nucleation. Starting from molecular simulations, we succeed in correctly predicting bulk thermodynamic quantities and experimental data, including equilibrium constants, titration curves, and detailed x-ray absorption spectra taken from the supersaturated CaCO3 solutions. The picture that emerges is in complete agreement with classical views of cluster populations in which ions and ion pairs dominate, with the concomitant free energy landscapes following classical nucleation theory