Lucia Carlucci

Polycatenation, polythreading and polyknotting in coordination network chemistry

The use of crystal engineering concepts has produced a variety of coordination networks, many of which exhibit novel and fascinating types of entanglements of individual motifs. This review analyses the structures of a number of entangled polymeric networks reported in these years by many groups. A topological classification of the different interlocked and interweaved species is attempted. Wide classes of polycatenated and polythreaded species have been recognized and other phenomena, as polyknotting (self-penetration) and interweaving of 1D chains, are also discussed. Unexpected topological features and new linkages, that were previously overviewed, have been discovered, including the first examples of infinite Borromean links.

Interpenetrating metal–organic and inorganic 3D networks: a computer-aided systematic investigation. Part I. Analysis of the Cambridge structural database

The occurrence of interpenetration in metal–organic and inorganic networks has been investigated by a systematic analysis of the CSD and ICSD structural databases. For this purpose, a novel version of TOPOS (a program package for multipurpose crystallochemical analysis) has been employed, where the procedure of recognition of interpenetrating nets is based on the representation of a crystal structure as a finite reduced graph. In this paper we report a comprehensive list (301 Refcodes) of interpenetrating metal–organic 3D structures from CSD, that are analyzed on the basis of their topologies. Interesting trends and novel features have been observed and distinct classes of interpenetrating nets have been envisaged, depending on the relationships of the individual motifs.

Borromean links and other non-conventional links in ‘polycatenated’ coordination polymers: re-examination of some puzzling networks

A number of coordination networks, exhibiting novel and fascinating types of entanglements of individual motifs have been reported throughout the years by many groups. The structural complexity of these species has caused, in some cases, misinterpretations regarding the correct nature of the entanglement. In this article, we analyse the structures of some polymeric networks of the ‘polycatenanes’ class, which have the peculiar feature of all the constituent motifs having lower dimensionality than that of the overall array. Unexpected topological features and new linkages, that had previously been overlooked, have been discovered. The most relevant finding concerns the first observation of examples of Borromean links in 3D and 2D arrays. These systems are comprised of layers that are not catenated but, nonetheless, inseparably entangled in an uncommon topological fashion.

Complex Interwoven Polymeric Frames from the Self‐Assembly of Silver(I) Cations and Sebaconitrile

Interwoven networks have been isolated from the self-assembly of the flexible long-chain sebaconitrile (1,10-decanedinitrile) and different silver(I) salts. These networks include an eightfold interpenetrated diamondoid frame (I), a fourfold interwoven 3D four-connected frame topologically related to the prototypical SrAl2 (II), an infinitely catenated 2D multilayer (III), and a 3D entangled array (IV).

A new type of entanglement involving one-dimensional ribbons of rings catenated to a three-dimensional network in the nanoporous structure of [Co(bix)2(H2O)2](SO4)·7H2O [bix = 1,4-bis(imidazol-1-ylmethyl)benzene]

Co(II) sulfate reacts with the flexible ligand 1,4-bis(imidazol-1-ylmethyl)benzene (bix) to yield the coordination network [Co(bix)2(H2O)2](SO4).7H2O, containing polymeric ribbons of rings which penetrate and catenate a 3D single frame of the CdSO4 topology, to produce an open-channel entangled architecture with nanoporous behaviour.

New polymeric networks from the self-assembly of silver(I) salts and the flexible ligand 1,3-bis(4-pyridyl)propane (bpp). A systematic investigation of the effects of the counterions and a survey of the coordination polymers based on bpp

The self-assembly of polymeric networks from different Ag(I) salts and the flexible ligand 1,3-bis(4-pyridyl)propane (bpp) has been systematically investigated in order to obtain some basic information useful for the crystal engineering of coordination frames upon variation of the counterions. The salts AgNO3, AgBF4, AgClO4, AgPF6, AgAsF6 and AgSbF6 have been reacted in the molar ratio Ag∶bpp of 1∶2. Though in some cases we have observed the formation of mixtures, containing also minor amounts of the 1∶1 adducts [Ag(bpp)]X, the [Ag(bpp)2]X derivatives have been obtained for all the salts, and all of the isolated crystalline products have been characterized by single-crystal X-ray analysis. Polymeric 2D and 3D networks have been observed, exhibiting four different structural motifs: [Ag(bpp)2](NO3) (1) contains 2D layers of square meshes that show 2-fold parallel interpenetration; compounds [Ag(bpp)2](BF4) (2) and [Ag(bpp)2](ClO4) (3) are isomorphous and contain 2-fold interpenetrated diamondoid networks; more surprisingly, compounds [Ag(bpp)2](PF6) (4) and [Ag(bpp)2](AsF6) (5) show a wafer-like structure containing, for the first time, 2-fold entangled (4,4) layers alternated to simple (4,4) layers; and finally, [Ag(bpp)2](SbF6) (6) contains single 2D layers of tessellated 4-membered rings. A brief analysis of the known coordination polymers based on the bpp ligand is also reported, including the structure of the novel species [Cu(NO3)2(bpp)]2·2CH2Cl2, a molecular ring that represents the unique example showing the GG conformation for the bpp ligands.

Entangled Two-Dimensional Coordination Networks: A General Survey

Survey Lucia Carlucci,*,† Gianfranco Ciani,† Davide M. Proserpio,*,†,‡ Tatiana G. Mitina,‡ and Vladislav A. Blatov*,‡,§ †Dipartimento di Chimica, Universita ̀ degli Studi di Milano, Via C. Golgi 19, 20133 Milano, Italy ‡Samara Center for Theoretical Materials Science, Samara State University, Ac. Pavlov Street 1, Samara 443011, Russia Chemistry Department, Faculty of Science, King Abdulaziz University, Post Office Box 80203, Jeddah 21589, Saudi Arabia

Interpenetrating diamondoid frameworks of silver( I ) cations linked by N , N ′-bidentate molecular rods

Three novel coordination polymers, [Ag(N–N)2]X (N–N = 4,4′-bipyridyl, X = CF3SO3––1; N–N = 4-cyanopyridine, X = BF4–, in two polymorphs, 2 and 3)], are prepared and investigated by single crystal X-ray analysis; 1 and 2 contain three-dimensional cationic frameworks, both consisting of four equivalent interpenetrating diamondoid lattices, while 3 is formed by two-dimensional layers of distorted squares.

Interpenetrated three-dimensional hydrogen-bonded networks from metal–organic molecular and one- or two-dimensional polymeric motifs

The occurrence of interpenetrated three-dimensional networks has been systematically investigated by the analysis of the crystallographic structural databases, using the program package TOPOS. After our previous reports on interpenetration observed in valence-bonded MOFs, inorganic arrays and hydrogen-bonded organic supramolecular architectures, in this paper we have focused our research on the interpenetrated 3D networks based on hydrogen-bonded metal–organic molecular (0D) and polymeric (1D and 2D) complexes from the Cambridge Structural Database. The current interest for the crystal engineering of new functional materials has prompted many research groups to adopt synthetic strategies implying the use of molecular metal complexes (0D) with suitably exo-oriented hydrogen-bond donor and acceptor groups for the assembly of extended networks. With regard to this we have examined 3D hydrogen-bonded supramolecular arrays formed by finite and infinite motifs of lower dimensionality, analyzing their topologies and looking for their entanglements. We have extracted a comprehensive list including 135 different motifs (71 assembled from 0D, 43 from 1D and 21 from 2D metal–organic motifs) showing the phenomenon of interpenetration (about two thirds not detected in the original papers). These hydrogen-bonded networks include species assembled by one or more building blocks, that are classified within the previously introduced Classes of interpenetration. It is observed that the maximum interpenetration degree is limited to 5-fold and the main (overall) topology is 412.63-pcu. An analysis of the possible relationships between the dimensionality of the building blocks and the resulting network connectivity and topology, and of some factors determining the interpenetration is also attempted, together with a comparison of the present results with those for other families of interpenetrated materials.

Supramolecular isomers in the same crystal: a new case involving two different types of layers polycatenated in the 3D architecture of [Cu(bix)2(SO4)]·7.5H2O [bix = 1,4-bis(imidazol-1-ylmethyl)benzene]

The reactions of copper(II) sulfate with the flexible ligand 1,4-bis(imidazol-1-ylmethyl)benzene (bix) in H2O/acetone solution have afforded two novel coordination polymers, i.e. the 1D species [Cu(bix)(H2O)3(SO4)]·H2O and the 3D networked array [Cu(bix)2(SO4)]·7.5H2O. The former polymer contains highly undulated chains that are joined into 2D layers via hydrogen bond bridges. The second species shows an unusual 3D architecture comprised of two interlocked sets of different 2D layers, giving inclined polycatenation. Both sets of layers display the same (4,4) topology but exhibit quite different tiling patterns (with ‘ideal’ plane symmetry c2mm and p4gm, respectively) because of the varied conformations of the bix ligands on passing from the first set to the second one. These two 2D motifs represent a new case of supramolecular isomerism in the same crystal. The sulfate anions form μ2-bridges between copper ions, that cross-link the two sets of layers, giving a single 3D self-penetrating 6-connected network. This shows channels (total free void ca. 27% of the cell volume) containing many solvated water molecules, that are lost upon thermal activation and regained with crystal modification. A brief analysis of the known examples of supramolecular isomers contained in the same crystal is also reported.