2-Acetyl­pyridinium 3-amino-2-chloro­pyridinium tetra­chloridocobaltate(II)

In the title complex, (C5H6ClN2)(C7H8NO)[CoCl4], the CoII ions are tetra­hedrally coordinated. The crystal structure is built from hydrogen-bonded centrosymmetric tetra­mers of tetra­chloridocobaltate(II) dianions and 3-amino-2-chloro­pyridinium cations, additionally strengthened by significant π–π stacking of pyridinium rings [interplanar distance 3.389 (3) Å]. The tetra­mers are linked by N—H⋯Cl hydrogen bonds into chains; the second kind of cations, viz. 2-acetyl­pyridinium, are connected by N—H⋯Cl hydrogen bonds to both sides of the chain. The Co—Cl bond lengths in the dianion correlate with the number of hydrogen bonds accepted by the Cl atom. An intramolecular C—H⋯Cl interaction is also present

Chlorido[2,15-dimethyl-3,7,10,14,20-penta­azabicyclo­[14.3.1]eicosa-1(20),2,14,16,18-penta­ene]manganese(II) perchlorate acetonitrile solvate

The Mn ion in the title complex, [MnCl(C17H27N5)]ClO4·CH3CN, is six-coordinated with a geometry inter­mediate between penta­gonal pyramidal and heavily distorted octa­hedral. In the macrocycle, the pyridinium ring makes a large dihedral angle of 63.70 (9)° with the best plane through the remaining four N atoms. This feature is common for 17-membered N5 rings, in contrast to their 16- and 15-membered analogues which often form planar N5 systems. In the crystal, N—H⋯O and C—H⋯O interactions help to establish the packing. The perchlorate counter-ion is rotationally disordered around the chlorine centre, with occupation factors of 0.74 (1) and 0.26 (1)

Imine-Based Architectures at Surfaces and Interfaces: From Self-Assembly to Dynamic Covalent Chemistry in 2D

Within the last two decades, dynamic covalent chemistry (DCC) has emerged as an efficient and versatile strategy for the design and synthesis of complex molecular systems in solution. While early examples of supramolecularly assisted covalent synthesis at surfaces relied strongly on kinetically controlled reactions for post-assembly covalent modification, the DCC method takes advantage of the reversible nature of bond formation and allows the generation of the new covalently bonded structures under thermodynamic control. These structurally complex architectures obtained by means of DCC protocols offer a wealth of solutions and opportunities in the generation of new complex materials that possess sophisticated properties. In this focus review we examine the formation of covalently bonded imine-based discrete nanostructures as well as one-dimensional (1D) polymers and two-dimensional (2D) covalent organic frameworks (COFs) physisorbed on solid substrates under various experimental conditions, for example, under ultra-high vacuum (UHV) or at the solid–liquid interface. Scanning tunneling microscopy (STM) was used to gain insight, with a sub-nanometer resolution, into the structure and properties of those complex nanopatterns

Photoisomerisation and light-induced morphological switching of a polyoxometalate–azobenzene hybrid

The functionalization of a spherical Keplerate-type polyoxometalate {Mo72V30} with a cationic azobenzene surfactant has been achieved through ionic self-assembly. The photoisomerisation reaction of this complex, which emerges in a light-triggered aggregation–disaggregation process, has been followed by 1H NMR spectroscopy, dynamic light scattering, absorption spectroscopy and scanning electron microscopy analyses

Molecular Squares, Coordination Polymers and Mononuclear Complexes Supported by 2,4-Dipyrazolyl-6H-1,3,5-triazine and 4,6-Dipyrazolylpyrimidine Ligands

The Fe[BF4]2 complex of 2,4-di(pyrazol-1-yl)-6H-1,3,5-triazine (L1) is a high-spin molecular square, [{Fe(L1)}4(μ-L1)4][BF4]8, whose crystals also contain the unusual HPzBF3 (HPz = pyrazole) adduct. Three other 2,4-di(pyrazol-1-yl)-6H-1,3,5-triazine derivatives with different pyrazole substituents (L2-L4) are unstable in the presence of first row transition ions, but form mononuclear, polymeric or molecular square complexes with silver(I). Most of these compounds involve bis-bidentate di(pyrazolyl)triazine coordination, which is unusual for that class of ligand, and the molecular squares encapsulate one or two BF4‒, ClO4‒ or SbF6‒ ions through combinations of anion...π, Ag...X and/or C‒H...X (X = O or F) interactions. Treatment of Fe[NCS]2 or Fe[NCSe]2 with 4,6-di(pyrazol-1-yl)-2H-pyrimidine (L5) or its 2-methyl and 2-amino derivatives L6 and L7) yields mononuclear [Fe(NCE)2L2] and/or the 1D coordination polymers catena-[Fe(NCE)2(μ-L)] (E = S or Se, L = L5-L7). Alcohol solvates of isomorphous [Fe(NCS)2L2] and [Fe(NCSe)2L2] compounds show different patterns of intermolecular hydrogen bonding, reflecting the acceptor properties of the anion ligands. These iron compounds are all high-spin, although annealing solvated crystals of [Fe(NCSe)2(L5)2] affords a new phase exhibiting an abrupt, low-temperature spin transition. Catena-[Fe(H2O)2(μ-L5)][ClO4]2 is a coordination polymer of alternating cis and trans iron centres