This critical review presents a comprehensive study of transition-metal carboxylate clusters which may serve as secondary building units (SBUs) towards construction and synthesis of metal–organic frameworks (MOFs). We describe the geometries of 131 SBUs, their connectivity and composition. This contribution presents a comprehensive list of the wide variety of transition-metal carboxylate clusters which may serve as secondary building units (SBUs) in the construction and synthesis of metal–organic frameworks. The SBUs discussed here were obtained from a search of molecules and extended structures archived in the Cambridge Structure Database (CSD, version 5.28, January 2007) which included only crystals containing metal carboxylate linkages (241 references).

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Secondary building units, nets and bonding in the chemistry of metal–organic frameworks

Coordination polymer networks with O- and N-donors: What they are, why and how they are made

This review (over 380 references) summarizes metal–organic frameworks (MOFs), Materials Institute Lavoisier (MILs), iso-reticular metal–organic frameworks (IR-MOFs), porous coordination networks (PCNs), zeolitic metal–organic frameworks (ZMOFs) and porous coordination polymers (PCPs) with selected examples of their structures, concepts for linkers, syntheses, post-synthesis modifications, metal nanoparticle formations in MOFs, porosity and zeolitic behavior for applications in gas storage for hydrogen, carbon dioxide, methane and applications in conductivity, luminescence and catalysis.

MOFs, MILs and more: concepts, properties and applications for porous coordination networks (PCNs)

This review is essentially an update of one entitled “πBonding and The Lone Pair Effect in Multiple Bonds Between Heavier Main Group Elements” which was published more than 10 years ago in this journal.1 The coverage of that survey was focused on the synthesis, structure, and bonding of stable compounds2 of heavier main group elements that correspond to the skeletal drawings reproduced in Tables 1 and 2. A row of numbers is listed at the bottom of each column in these tables. This refers to the number of stable complexes from each class that are currently known. The numbers in parentheses refer to the number of stable species that were known at the time of the previous review. Clearly, many of the compound classes listed have undergone considerable expansion although some remain stubbornly rare. The most significant developments for each class will be discussed in detail under the respective sections. As will be seen, there are also a limited number of multiple bonded heavier main group species that do not fit neatly in the classifications in Tables 1 and 2. However, to keep the review to a manageable length, the limits and exclusions, which parallel those used earlier, are summarized as follows: (i) discussion is mainly confined to compounds where experimental data on stable, isolated species have been obtained, (ii) stable compounds having multiple bonding between heavier main group elements and transition metals are not generally discussed, (iii) compounds in which a multiple bonded heavier main group element is incorporated within a ring are generally not covered, and (iv) hypervalent main group compounds that may incorporate faux multiple bonding are generally excluded. Such compounds are distinguished from those in Tables 1 and 2 in that they apparently require the use of more than four valence bonding orbitals at one or more of the bonded atoms. The remainder of this review is organized in a similar manner to that of the previous one wherein the compounds to be discussed are classified according to those summarized in Tables 1 and 2. The key unifying feature of almost all molecules discussed in this review is that they are generally stabilized by the use of bulky substituents which block associative or various decomposition pathways.3 Since the previous review was published in 1999, several review articles that cover parts of the subject matter have appeared.4

π-Bonding and the Lone Pair Effect in Multiple Bonds Involving Heavier Main Group Elements: Developments in the New Millennium

Triazoles and tetrazoles: Prime ligands to generate remarkable coordination materials

Self-assembly of Cd(II), 1,3-di(4-pyridyl)propane and 5-sulfoisophthalic acid monosodium salt in CH3OH–H2O solution produced a supramolecular open framework with 1D channels that encapsulates an infinite chain consisting of water decamers linked by Cd2+.

(H2O)12-containing infinite chain encapsulated in supramolecular open framework built of cadmium(II), 1,3-di(4-pyridyl)propane and 5-sulfoisophthalic acid monosodium salt

For the first time, a dimer of deltahedral Zintl ions is made. Interest in synthesis, isolation, and characterization of deltahedral Zintl ions from solutions dates back to the 19th century, 1 and many such species have been discovered since. 2-6 Most of them are deltahedral, and all of them are monomeric. Well-established species among the deltahedra are the nine-atom nido clusters of group 14, such as Ge 9, Sn9, and Pb9, monocapped square antiprisms with classical electron counts according to the Wade’s rules.7 More recently, the same types of clusters were proven to exist in the neat solids that were used as precursors to the solution studies. 8,9 In addition to these, known are also the one-electron oxidized versions, i.e., cluster radicals of the same or similar geometries but charge of 3 -.2,3 Here we report on the coupling of deltahedral nine-atom clusters into dimers in a formal oxidative coupling reaction. Dimers of Ge 9-Ge9 are found in the compound Cs4(K-crypt)2[(Ge9)-(Ge9)]‚6en(1), where en is ethylenediamine and crypt is 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane. Crystals of1 in high yield were initially made by precipitation of a solution of a precursor of nominal composition K 2CsGe14B3 in ethylenediamine and excess of crypt. 10 Later, a precursor without boron, Cs 2KGe9, was used. The solutions are green-brown and form instantly upon addition of the precursor to the mixture of ethylenediamine and crypt. 11 It should be noted here that the solutions from which most previously known compounds of germanium clusters were crystallized were reportedly red to redbrown.2-4 The only other report of brownish green color was for a precursor of nominal composition “NaGe 2.25” dissolved in ethylenediamine. 5 At this stage, it is not clear what causes the different colors. Single crystals of 1 grow on the walls of the vessels and become visible by naked eye within a few hours. No other phases form. After a day, most of the crystals are of sizes that are good enough for single-crystal X-ray diffraction studies. Such crystals were selected and mounted in glass capillaries, and the structure was determined from data collected on one of them. 12 The new compound contains dimers made of two Ge 9 clusters that are connected via an exobond between two vertexes (Figure 1). The two halves are identical since there is an inversion center at the midpoint of the bond connecting them. The geometry of the Ge9 cluster is very close to the classical monocapped square antiprism that is expected for nido deltahedral clusters of nine atoms. Often such shape assignments are questioned since the borderline between this shape and that of a tricapped trigonal prism is not clear. For this particular cluster, however, the established criteria unequivocally indicate monocapped square antiprism. 2,6 For example, the two dihedral angles at the open square base are 1.08 and 1.15 °, and this means that the square is virtually planar, as in an ideal monocapped square antiprism. The diagonals in the base are 3.433(1) and 3.848(1) Å for Ge6 -Ge8 and Ge7-Ge9, respectively. They are somewhat different due to the shorter distances around the exo-bonded atom Ge6, two bonds of 2.525(1) Å, compared to the other two distances in the square, 2.640(1) and 2.628(1) Å for Ge8 -Ge7 and Ge8 -Ge9, respectively. This is most likely a direct result of having an exobond at Ge6 instead of a lone pair and the lesser repulsion associated with that. The averaged distances within the clusters of 1 are nearly identical with those of Ge 9 clusters found in (Kcrypt)6Ge9Ge9 (2), which contains Ge 9 and Ge9, Rb4Ge9‚en (3),5 and the neat Cs 4Ge9 (4).8a The average distances around the capping atom ( dcap), at the capped square ( dcsq), at the open square (dosq), and at the waist ( dwst) for the four compounds are (compound number in parentheses) as follow: dcap ) 2.578 (1), 2.563 (2), 2.56 (3), and 2.572 ( 4) Å; dcsq ) 2.810 (1), 2.807 (2), 2.84 (3), and 2.828 ( 4) Å; dosq ) 2.580 (1), 2.553 (2), 2.57 (3), and 2.590 ( 4) Å; and dwst ) 2.604 (1), 2.595 (2), 2.58 (3), and 2.590 (4) Å. The two clusters are connected by an exobond between two Ge6 atoms that are vertexes in the open squares. The distance, 2.488(2) Å, indicates a simple two-center, two-electron localized bond. It can be compared with the distance in elemental germanium, 2.445 Å, and the average Ge -Ge distances in CsNa 2Ge17 with the clathrate-II structure, 2.494 Å, 14 and in K4Ge23-x with the clathrate-I structure, 2.502 Å. 15 It is clearly longer than that in the element, which can be easily explained with the higher coordination number of Ge6 in the clusters, where it is surrounded by five germanium atoms and a cesium cation. On the other hand, it is shorter than the bonds in the clathrates, although the germanium atoms are only four-bonded in the latter. The reason in this case is most likely electronic since the clathrates have extra electrons provided by the alkali metals that are delocalized over the germanium antibonding band (the conduction band). 14

Oxidative Coupling of Deltahedral [Ge9]4- Zintl Ions

Mid-far infrared (IR) non-linear optical (NLO) materials are of great importance in military and civil fields. However, commercial IR-NLO crystals (such as AgGaS2, AgGaSe2 and ZnGeP2) do not currently satisfy the requirements of large second-harmonic generation (SHG) and high laser induced damage thresholds (LIDTs), which seriously limits their practical applications. Herein, we have developed a new series of salt-inclusion chalcogenides, [A3X][Ga3PS8] (A = K, Rb; X = Cl, Br), which are constructed from alternate stacking of adamantane-like [Ga3PS10]6− cluster layers and cationic [A3X]2+ salt layers. Importantly, they display both large SHG responses of several-fold and high LIDTs for dozens of times that of commercial AgGaS2, which exhibit the highest LIDTs among the reported IR-NLO materials with a larger SHG conversion efficiency than that of AgGaS2. These properties together with wide transparent region, type I phase-matching features and congruent-melting behaviors indicate they are promising IR-NLO materials.

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[A3X][Ga3PS8] (A = K, Rb; X = Cl, Br): promising IR non-linear optical materials exhibiting concurrently strong second-harmonic generation and high laser induced damage thresholds

Two new PbII–SIP coordination polymers, {[Pb4(OH)2(SIP)2(H2O)](H2O)5}n (1) and [Pb3(SIP)2(H2O)5]n (2), have been synthesized by hydrothermal reactions of Pb(OH)2 or Pb(NO3)2 and 5-sulfoisophthalic acid monosodium salt (NaH2SIP) at 160 °C, respectively. Single-crystal X-ray diffraction reveals that compound 1 has a 2D brick-wall-like architecture constructed from 1D tapes containing the basketlike tetranuclear [Pb4(μ3-OH)2(COO)2]. Compound 2 has a 2D-layered structure, which is constructed from a 1D-ladder structure composed of the cyclic [Pb4(SIP)2(COO)2] grid with the four Pb atoms nearly coplanar. In the solid state, compound 1 exhibits blue photoluminescence with the maximum emission intensity at 436 nm upon excitation at 335 nm. Compound 2 shows phosphorescence with the maximum emission intensity at 603 nm upon excitation at 426 nm. Both compounds have also been characterized by elemental analysis, IR spectra, TG analysis, and powder X-ray diffraction. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Synthesis, Crystal Structures, and Photophysical Properties of Two Novel Lead(II)–SIP Coordination Polymers (NaH2SIP = 5-Sulfoisophthalic Acid Monosodium Salt) Containing Tetranuclear Lead(II) Units

Hydrothermal synthesis of a series of copper(II)−H3SIP coordination polymers (H3SIP = 5-sulfoisophthalic acid), [Cu3(SIP)2(H2O)14] (1), {[Cu(SIP)(H2O)4](H2en)0.5}n (2), {Na[Cu2(SIP)(HSIP)(H2O)8](H2O)3}n (3), {[Cu4(OH)2(SIP)2(H2O)2](H2O)4}n (4), [Cu2(OH)(SIP)(bpy)(H2O)]n (5), [Cu4(OH)2(SIP)2(bpy)3(H2O)]n (6), and [Cu4(OH)2(SIP)2(bpy)2(H2O)2]n (7) (bpy = 2,2‘-bipyridine; en = ethylenediamine), has been achieved by fine control over the reaction conditions including pH value, organic template, reaction temperature, starting materials, auxiliary ligand, and stoichiometry. X-ray structural analyses of 1−7 reveal their structural diversity ranging from zero-dimensional (0-D) (1), one-dimensional (1-D) (2), two-dimensional (2-D) (3, 5, and 6), to three-dimensional (3-D) (4 and 7). The relationship between the reaction conditions and the resulting structures has been rationalized. The trinuclear complex 1 represents the first example of a discrete metal−SIP coordination complex. The presence of countercations suc...

Li Xu

Papers

(H2O)12-containing infinite chain encapsulated in supramolecular open framework built of cadmium(II), 1,3-di(4-pyridyl)propane and 5-sulfoisophthalic acid monosodium salt

Oxidative Coupling of Deltahedral [Ge9]4- Zintl Ions

[A3X][Ga3PS8] (A = K, Rb; X = Cl, Br): promising IR non-linear optical materials exhibiting concurrently strong second-harmonic generation and high laser induced damage thresholds

Synthesis, Crystal Structures, and Photophysical Properties of Two Novel Lead(II)–SIP Coordination Polymers (NaH2SIP = 5-Sulfoisophthalic Acid Monosodium Salt) Containing Tetranuclear Lead(II) Units

Diversity of Coordination Architecture of Copper(II)−5-Sulfoisophthalic Acid: Synthesis, Crystal Structures, and Characterization