Three new organic tectons (2–4) based on the p-tert-butylthiacalix4arene backbone, blocked in the 1,3-alternate conformation, bearing four pyridyl coordinating moieties, have been synthesised and ...characterised in the solid state. The ligands are positional isomers and differ by the position of the N atom on the pyridyl unit (ortho for 2, meta for 3 and para for 4). Their combination with the Ag+ cation leads, reproducibly, to the formation of 2- and 3-D infinite silver coordination networks. Independent of the nature of the anion, the combination of 2 offering four (N,S) type chelates with the Ag+ cation affords an unprecedented diamond type 3D network. Both 3 and 4, behaving as tetrakis monodentate ligands, lead to the formation of 2-D architectures.
One may apply concepts developed in the context of molecular recognition of anions by synthetic receptors in solution to the design of molecular tectons capable of generating molecular networks with ...anionic species in the crystalline phase. With respect to that, bis-cyclic amidinium dications are interesting tectons because they offer two positive charges allowing strong electrostatic charge–charge interactions with anions and four acidic protons divergently oriented and capable of forming two sets of two H-bond chelates. The latter characteristic is of interest for the generation of supramolecular chirality taking place within the second coordination sphere around anionic metal complexes adopting an octahedral coordination geometry.
Combinations of six new coordinating tectons ( 3–8 ) tetrakis-pyrazolyl appended calix4arenes, blocked in 1,3-A conformation, based on 1 (tetrathiacalix4arene) and 2 ...(tetrathiatetramercaptocalix4arene) derivatives, with AgX salts (X = NO 3 − , BF 4 − , XF 6 − (X = P, As and Sb)) lead to nine new silver coordination networks. The flexible nature of tectons 3–8 (length of the spacer between the macrocycle and the pyrazolyl coordinating unit), their high number of potential coordinating sites and the loose coordination demand of Ag + cation lead to the formation of a large variety of networks with different dimensionality: from 1D ( 5 -AgSbF 6 , 5 -AgBF 4 , 7 -AgSbF 6 and 8 -AgNO 3 ) to extended 2D ( 6 -AgBF 4 and 8 -AgSbF 6 ) and to a series of three isostructural porous diamond-like 3D architectures ( 6 -AgXF 6 (X = P, As and Sb)).
A series of thiacalix4arene derivatives blocked in the 1,3-alternate conformation and bearing four carboxylic acids have been designed and synthesized. These compounds, owing to the H-bond donor (OH ...moiety) and acceptor (C&z.dbd; O group) nature of the carboxylic acid moieties, behave as self-complementary tectons and lead to the formation of tubular 1D H-bonded networks in the crystalline phase. Upon deprotonation of the self-complementary neutral compounds, i.e. transformation of carboxylic acid moieties into carboxylates, anionic tectons are generated. Due to their propensity to form H-bonded networks in the presence of a dicationic H-bond donor tecton of the cyclic bis-amidinium type, designed to behave as a molecular staple interconnecting two carboxylates moieties, 1- and 2-D H-bonded networks are formed under self-assembly conditions.
Two new ligands, one symmetric 1 and the other acentric 2, based on a porphyrin backbone bearing either two ethynylpyridyl or one pyridyl and one ethynylpyridyl coordinating groups connected to the ...porphyrin at two opposite meso positions have been designed and prepared. In the presence of a Zn(II) cation, they lead to the formation of neutral metallatectons 1-Zn and 2-Zn which self-assemble into coordination networks in the crystalline phase. Whereas the metallatecton 1-Zn leads exclusively to the formation of grid type 2D networks, 2-Zn generates two types of crystals with rod and rhombic morphologies. The rod type crystals are composed of a 1D zigzag type arrangement whereas crystals with rhombic morphology are composed of directional 2D grid type architecture. The packing of the latter leading to the formation of the crystal occurs in a centrosymmetric fashion causing thus the loss of directionality.
Interaction and integration of uncertainties in on-site and off-site project activities often result in the risk of delays and schedule overruns in hybrid construction projects. To address this ...problem, a holistic risk analysis approach that assesses the integrating impact of uncertainties on completion times is proposed. The results of the analysis show that growth in project size and work quantities intensifies pair and group interconnection of tasks within and between groups of on-site and off-site activities, resulting in lengthened completion times and deviations from project plans. Unavailability of resources, risk seeking attitudes, and workflow variability are other major contributors to the risk of late completion in hybrid construction. While project managers often analyze on-site and off-site uncertainties separately, practical implications of the research results suggest adoption of a holistic approach in which risk management practices in the two environments are integrated. This approach significantly improves tangible performance measures in projects.
•Growth in off-site and on-site work quantities increases the risk of deviations from project plan.•Targeted level of project plan reliability in hybrid construction is determined by organization's risk appetite.•Late completion risk in hybrid construction has an inverse relationship with targeted project plan reliability.•Availability of resources in both off-site and on-site activities significantly decreases the late completion risk.•Risk of deviations from project plan has a direct relationship with combined level of workflow variability.
Combinations of tetramercaptotetrathiacalix4arene pyridyl-appended positional isomers with HgCl2 lead to the formation of neutral coordination networks with their dimensionality imposed by the ...position of the N atom on the pyridyl group.
The combination of the same organic tecton 1, a meta-pyridyl appended tetramercaptotetrathiacalix4arene in 1,3-alternate conformation offering four pyridyl units and eight thioether groups, with ...three silver salts AgX (X = BF4(-), NO3(-) and SbF6(-)) leads, under identical conditions (concentration, temperature and solvent system), to the formation of different silver coordination networks. Both the connectivity and the dimensionality of the three silver coordination networks depend on the nature of the anion used as a counter ion. Whereas the weakly coordinating BF4(-) anion does not participate in the formation of the non-tubular 1D coordination network, the coordinating NO3(-) anion is bound to the metal cation and this leads to the formation of a tubular 1D silver coordination network. In both cases, the eight S atoms of the tecton 1 do not take part in the binding of the cation. In marked contrast, when the SbF6(-) anion is used as a counter ion, the organic tecton 1 behaves as a tetrakismonodentate through its four meta-pyridyl moieties and as a bischelating unit of the SCCS type leading thus to the formation of a porous 3D diamondoid-type network.
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