The bottom-up construction of highly functional metallamacrocycles from simple building blocks is a challenge of much current interest. We have used solvothermal reactions of a bifunctional p-bitmb ligand with [Ru(arene)X2]2 in CH2Cl2 or CH2Br2 to generate the novel mononuclear metallamacrocyclic [RuX(arene)L2CH2]X3 complexes 1–3 (1, arene = p-cym, X = Cl; 2, arene = bip, X = Cl; 3, arene = p-cym, X = Br), which were characterized by various techniques. These complexes are “bowl-like” and have two faces: one coordinative Ru centre (arene)Ru(N,N)X bridged by L (L = 1,4-bis(imidazol-1-ylmethyl)-2,3,5,6-tetramethylbenzene, p-bitmb) to a dipositive bis-imidazolinium centre. Cl− or Br− anions can be trapped inside the cavity of the “bowl-like” structure, forming H-bonds with the backbone. Experimental (NMR and ESI-MS) and computational (DFT calculations) studies show that the source of the bridging –CH2– group is the dihalogenated solvent (CH2Cl2 or CH2Br2) that links the two arms of an initially formed non-cyclic complex (arene)RuX2L2 by a mechanism of nucleophilic substitution. Optimization of the reaction conditions afforded the macrocyclic complexes in almost quantitative yields. The applications of these complexes as anti-proliferative agents towards cancer cells and for selective anion sensing have been explored.

A facile solvothermal reaction was developed to synthesize α-Fe2O3 nanocrystals at relatively low temperature in the presence of small organic compound 2,4,6-tris(pyrazol-1-yl)-1,3,5-triazine (Tptz) as template. α-Fe2O3 nanocrystals with three different morphologies were obtained by simply changing the volume ratio of the reaction solvents, N,N-dimethylformamide (DMF) and H2O. The purities and morphologies of these samples were characterized by powder X-ray diffraction (PXRD), infrared spectrum (IR), high-resolution transmission electron microscopy (HRTEM) and field emission scanning electron microscopy (FESEM). It is remarkable that both the template Tptz ligand and the volume ratios of the mixture solvents are playing very significant roles for the formation and the morphological control of the products in this work. Furthermore, Congo red adsorption experiment showed that the adsorption capacities increased in an order of the samples with morphologies of nanopolyhedra, nanorods and rice-shaped. And the determined maximum adsorption capacity is up to 161 mg g−1 for the rice-shaped α-Fe2O3, which has the biggest BET surface area of 110.2 m2 g−1. These α-Fe2O3 nanocrystals reported here may have the potential to use as low-cost and efficient adsorbent materials to remove organic pollutants from water.

A novel two-dimensional metal–organic framework has been constructed from Fe3+ and meso-tetra(4-imidazoyl)porphyrin, which can remain in saturated (~27.5 M) NaOH solution for a week. To the best of our knowledge, this is the first report of a MOF that is stable in saturated NaOH solution. The utilization of an imidazolyl-based porphyrin ligand and a high-valence metal is a new and promising strategy for constructing porphyrinic MOFs with ultra-high stability.

Highlights•An uncommon 3D structure and a W-shape-like 2D layer structure have been reported.•Using both flexible and rigid ligands is a strategy for construction of these novel structures.•Changing the positions of imidazole group results in different structures.•The optical properties are related to the local linker environment.Two new Cd(II) coordination polymers, [Cd(BDC)(m-bitmb)(H2O)] (1) and [Cd2(BDC)2(p-bitmb)1.5(H2O)2] (2), have been solvothermally synthesized by reacting cadmium sulfate and 1,4-benzenedicarboxylic acid (H2BDC) with flexible ligands 1,3-bis(1-imidazol-1-ylmethyl)-2,4,6-trimethylbenzene (m-bitmb) or 1,4-bis(1-imidazol-1-ylmethyl)-2,3,5,6-tetramethylbenzene (p-bitmb), respectively. Compound 1 shows an uncommon 3D 4-connected 66 topology, a distorted diamond structure, while compound 2 is a novel 2D (3,4)-connected W-shape-like layer framework with a novel (63·66) topology. 1 and 2 have different fluorescence and thermal properties. Compound 1 shows a ligand based fluorescence, while compound 2 shows a red-shifted emission compared to the ligands and is assigned to the ligand-to-ligand charge transfer (LLCT) emission. These results demonstrated the structure–property relationship of MOF material.Graphical abstractChanging the positions of imidazole group of the flexible ligands resulted in different structures and different luminescent behaviors.

Structural characterization of a Pd3(bitmb)4Cl6·Pd2(bitmb)4Cl4·18H2O·2CH3OH (1) (bitmb = 1,3-bis(imidazol-1-ylmethyl)-2,4,6-trimethylbenzene) complex shows that it is a unique example of a co-crystal that includes both a M3L4 metallocage, Pd3(bitmb)4Cl6, and a M2L4 metallocage, Pd2(bitmb)4Cl4, in a 1:1 ratio. Single crystal analysis indicates that the structures of M3L4 and M2L4 in co-crystal 1 are almost identical to those of the free metallocages. However, both the M3L4 and M2L4 metallocages are flexible and their sizes and shapes can be mediated in co-crystal 1 by strong π⋯π interactions between the M3L4 and M2L4 metallocages, CH⋯Cl H-bonds between the M3L4 metallocages and so on. Such a packing mode may govern the formation of the M2L4 and M3L4 co-crystal complex in a 1:1 ratio. Furthermore, the combined reaction procedures allow the formation of 1 + 1 M2L4 and M3L4 co-crystal complex 1 in the solid state.

A nonporous neutral framework [CuCl2(m-bttmb)2]n (1) was changed into a porous ionic {[Cu(m-bttmb)2(H2O)Cl]Cl(CH3CN)0.5(H2O)2.75}n (2) by simply increasing the amount of CH3CN in the mixed solvent (CH3CN and H2O) or temperature in the reactions of CuCl2·2H2O with 1,3-bis(triazol-1-ylmethyl)-2,4,6-trimethylbenzene (m-bttmb). 1 undergoes transformation into 2 when treated with CH3CN. Both 1 and 2 have 2D 4-connected (4,4) network architectures but in different packing arrangements. These compounds have been characterized by single-crystal X-ray diffraction analysis, elemental analysis, IR spectra and thermogravimetric analysis. This work may provide a way to control the formation of neutral or ionic frameworks, as well as porosities by adjusting the polarity and components of the solvents.

A unique anionic 6-fold interpenetrated (10,3)-b Cd(II) framework was obtained using a novel nanosized tripodal aromatic acid ligand, in which both the Cd(II) atoms and tripodal aromatic acid ligands act as three-connected nodes. This compound displays intense and blue-shifted photoluminescence compared to that of the free H3L ligand.

DNA has a strong affinity for many heterocyclic aromatic dyes, such as acridine and its derivatives. Lerman in 1961 first proposed intercalation as the source of this affinity, and this mode of DNA binding has since attracted considerable research scrutiny. Organic intercalators can inhibit nucleic acid synthesis in vivo, and they are now common anticancer drugs in clinical therapy.The covalent attachment of organic intercalators to transition metal coordination complexes, yielding metallointercalators, can lead to novel DNA interactions that influence biological activity. Metal complexes with σ-bonded aromatic side arms can act as dual-function complexes: they bind to DNA both by metal coordination and through intercalation of the attached aromatic ligand. These aromatic side arms introduce new modes of DNA binding, involving mutual interactions of functional groups held in close proximity. The biological activity of both cis- and trans-diamine PtII complexes is dramatically enhanced by the addition of σ-bonded intercalators.We have explored a new class of organometallic “piano-stool” RuII and OsII arene anticancer complexes of the type [(η6-arene)Ru/Os(XY)Cl]+. Here XY is, for example, ethylenediamine (en), and the arene ligand can take many forms, including tetrahydroanthracene, biphenyl, or p-cymene. Arene−nucleobase stacking interactions can have a significant influence on both the kinetics and thermodynamics of DNA binding. In particular, the cytotoxic activity, conformational distortions, recognition by DNA-binding proteins, and repair mechanisms are dependent on the arene. A major difficulty in developing anticancer drugs is cross-resistance, a phenomenon whereby a cell that is resistant to one drug is also resistant to another drug in the same class. These new complexes are non-cross-resistant with cisplatin towards cancer cells: they constitute a new class of anticancer agents, with a mechanism of action that differs from the anticancer drug cisplatin and its analogs. The Ru−arene complexes with dual functions are more potent towards cancer cells than their nonintercalating analogs.In this Account, we focus on recent studies of dual-function organometallic RuII− and OsII−arene complexes and the methods used to detect arene−DNA intercalation. We relate these interactions to the mechanism of anticancer activity and to structure−activity relationships. The interactions between these complexes and DNA show close similarities to those of covalent polycyclic aromatic carcinogens, especially to N7-alkylating intercalation compounds. However, Ru−arene complexes exhibit some new features. Classical intercalation and base extrusion next to the metallated base is observed for {(η6-biphenyl)Ru(ethylenediamine)}2+ adducts of a 14-mer duplex, while penetrating arene intercalation occurs for adducts of the nonaromatic bulky intercalator {(η6-tetrahydroanthracene)Ru(ethylenediamine)}2+ with a 6-mer duplex. The introduction of dual-function Ru−arene complexes introduces new mechanisms of antitumor activity, novel mechanisms for attack on DNA, and new concepts for developing structure− activity relationships. We hope this discussion will stimulate thoughtful and focused research on the design of anticancer chemotherapeutic agents using these unique approaches.

The organometallic RuII arene complex [(η6-tha)Ru(en)Cl]+ (1), where tha = tetrahydroanthracene and en = ethylenediamine, is potently cytotoxic towards cancer cells. We have used a combination of HPLC, ESI-MS, 1D- and 2D-NMR, including [1H, 1H] ROESY, NOESY, [1H, 15N] HSQC (using 15N-1), and [1H, 31P] experiments to elucidate the role of the non-aromatic, bulky rings of tha in adducts with the DNA hexamer d(CGGCCG), since DNA is a potential target for this drug. Reactions of 1 with single-stranded d(CGGCCG) gave rise to ruthenation at each of the three G bases, whereas reactions of the duplex d(CGGCCG)2 with 1 mol equiv. 1 led to exclusive ruthenation of G3 and G6 (and G9, G12) and not G2 (or G8). Addition of a second mol equiv. of 1 gave di-ruthenated adducts (major sites G3/G6, G6/G9, G2/G6), and on reaction with a third mol equiv. tri-ruthenation (G2, G3/G6/G12).The NMR data are indicative of the coordinative binding of Ru-tha specifically to G3 and G6, together with penetrative intercalation of the bulky non-coordinated tha rings B and C of 1′, selectively between two base pairs G3/C10:C4/G9 and G6/C7:C5/G8. Intercalation at GpC base steps by tha has a lower energy penalty compared to intercalation at GpG base steps, thereby allowing accommodation of tha. Mono-intercalation of tha reduced the strength of H-bonding between en-NH and GO6. These differences in structural distortions compared to cisplatin induced by the coordinative binding of Ru-tha to GN7 may contribute to the differences in mechanism of action, including protein recognition of the metallated lesions, and lack of cross resistance.

Six coordination polymers, {[Ni(L1)2(H2O)2]·(H2O)4}n (1), {[Co(L1)2(H2O)2]·(H2O)4}n (2), [Co(L2)2]n (3), {[Hg3(L3)2Cl6]·(CH3OH)4·(H2O)2}n (4), {[Hg3(L3)2I6]·(H2O)3}n (5) and {[Zn3(L3)2Cl6]·(CH3OH)2·(H2O)4}n (6) (L1 = 3,5-bis(4-pyridylmethoxy)benzoate, L2 = 3,5-bis(3-pyridylmethoxy)benzoate, L3 = pyridin-4-ylmethyl-3,5-bis(pyridin-4-ylmethoxy)benzoate were synthesized under hydrothermal (solvothermal) conditions and structurally determined by single-crystal X-ray diffraction. 1 and 2 are isomorphous, exhibiting a double helical chain, in which L1 acts as a bidentate ligand to bridge two metal ions using the monodentate carboxylate group and one pyridyl arm. In complex 3, each L2 performs as a tridentate ligand using the chelating carboxylate group and one pyridyl arm to link two metal ions, forming a 2-D homochiral layer in which neighbouring helical chains with the same chirality are interlinked through metal ions. Complexes 4, 5 and 6 are constructed from ligand L3, which acts as a tridentate ligand to bridge three metal ions via three pyridyl arms. 4 and 5 are 1-D meso-helical chains but 6 is a zigzag chain. In 4, each HgCl2 connects with two L3 to form a helical subunit; neighbouring subunits are in opposite helicity and mediated by two other HgCl2 to form a chair-shaped conformation and this is extended into a double-chain network. 5 contains a helical half-a-turn reversal, which is constructed with two L3 linking two HgI2, showing a shell-like conformation. Complex 6 also contains shell-like conformations similar to those in 5, but it is a zigzag chain. The results indicate that the flexible/angular ligands can adopt different conformations, while the conformation restriction of flexible/angular ligands, together with the coordination preferences of the metal centers, plays a critical role in the construction of these novel coordination polymers.

Complexes [Cu2(bitmb)2Cl4] (1), [(CH3OH)(NO3)⊂Cu2(bitmb)4](NO3)3[(CH3OH)(NO3)⊂Cu2(bitmb)4](NO3)3 · CH3OH · 6 H2O (2) and [BF4⊂Cu2(bitmb)4][BF4⊂Cu2(bitmb)4](BF4)3 · 2 CH3OH · 4 H2O (3) are obtained by reaction of bitmb and Cu2+ salts with different anions (BF4-,NO3-orCl-) at different M:L ratio (1:1, 1:2 or 1:2). The results reveal that complex 1 is a neutral Cu2L2 rectangle and complexes 2 and 3 are M2L4 cage-like frameworks with an anion as guest. The anion competitive reaction of the Cu2L4 type receptor with tetrahedral, triangular and spherical anions (ClO4-,BF4-,NO3-andCl-) is reported. The anion competitive experiments demonstrate that the anion selective order is ClO4->BF4->NO3->Cl-, and ClO4- is the biggest and most preferable one, so far.The structures of a Cu2L2 rectangle and Cu2L4 cage complexes were reported and anion competitive reactions showed that the anion selective order is ClO4->BF4->NO3->Cl-, and ClO4- is the biggest and most preferable one, so far. This M2L4 cage receptor could selectively “recognize” anions of different size and shape in the solid state.

Complexes [PF6⊂(Ag3(titmb)2](PF6)2 (8) and {SbF6⊂[Ag3(titmb)2](SbF6)2}·H2O·1.5 CH3OH (9) are obtained by reaction of titmb and Ag+ salts with different anions (PF6− and SbF6−), and crystal structures reveal that they are both M3L2 cage complexes with short Ag⋯F interactions between the silver atoms and the fluorine atoms of the anions. In complex 8, a novel cage dimer is formed by weak Ag⋯F contacts; an unique cage tetramer formed via Ag⋯π interactions (Ag⋯η5-imidazole) between dimers and an infinite 1D cage chain is presented. However, each of the external non-disordered SbF6− anions connect with six cage 9s via Ag⋯F contacts, and each cage 9 in turn connects with three SbF6− anions to form a 2D network cage layer; and the layers are connected by π–π interactions to form a 3D network. The anion-exchange reactions of four Ag3L2 type complexes ([BF4⊂(Ag3(titmb)2](BF4)2 (6), [ClO4⊂(Ag3(titmb)2](ClO4)2 (7b), [PF6⊂(Ag3(titmb)2](PF6)2 (8) and [SbF6⊂(Ag3(titmb)2](SbF6)2·1.5CH3OH (9)) with tetrahedral and octahedral anions (ClO4−, BF4−, PF6− and SbF6−) are also reported. The anion-exchange experiments demonstrate that the anion selective order is SbF6− > PF6− > BF4−, ClO4−, and this anion receptor is preferred to trap octahedral and tetrahedral anions rather than linear or triangle anions; SbF6− is the biggest and most preferable one, so far. The dimensions of cage complexes with or without internal anions, anion-exchange reactions, cage assembly and anion inclusions, silver(I) coordination environments, Ag–F and Ag–π interactions of Ag3L2 complexes 1–9 are discussed.

Complexes [PF6⊂(Ag3(titmb)2](PF6)2 (8) and {SbF6⊂[Ag3(titmb)2](SbF6)2}·H2O·1.5 CH3OH (9) are obtained by reaction of titmb and Ag+ salts with different anions (PF6− and SbF6−), and crystal structures reveal that they are both M3L2 cage complexes with short Ag⋯F interactions between the silver atoms and the fluorine atoms of the anions. In complex 8, a novel cage dimer is formed by weak Ag⋯F contacts; an unique cage tetramer formed via Ag⋯π interactions (Ag⋯η5-imidazole) between dimers and an infinite 1D cage chain is presented. However, each of the external non-disordered SbF6− anions connect with six cage 9s via Ag⋯F contacts, and each cage 9 in turn connects with three SbF6− anions to form a 2D network cage layer; and the layers are connected by π–π interactions to form a 3D network. The anion-exchange reactions of four Ag3L2 type complexes ([BF4⊂(Ag3(titmb)2](BF4)2 (6), [ClO4⊂(Ag3(titmb)2](ClO4)2 (7b), [PF6⊂(Ag3(titmb)2](PF6)2 (8) and [SbF6⊂(Ag3(titmb)2](SbF6)2·1.5CH3OH (9)) with tetrahedral and octahedral anions (ClO4−, BF4−, PF6− and SbF6−) are also reported. The anion-exchange experiments demonstrate that the anion selective order is SbF6− > PF6− > BF4−, ClO4−, and this anion receptor is preferred to trap octahedral and tetrahedral anions rather than linear or triangle anions; SbF6− is the biggest and most preferable one, so far. The dimensions of cage complexes with or without internal anions, anion-exchange reactions, cage assembly and anion inclusions, silver(I) coordination environments, Ag–F and Ag–π interactions of Ag3L2 complexes 1–9 are discussed.

The organometallic RuII arene complex [(η6-tha)Ru(en)Cl]+ (1), where tha = tetrahydroanthracene and en = ethylenediamine, is potently cytotoxic towards cancer cells. We have used a combination of HPLC, ESI-MS, 1D- and 2D-NMR, including [1H, 1H] ROESY, NOESY, [1H, 15N] HSQC (using 15N-1), and [1H, 31P] experiments to elucidate the role of the non-aromatic, bulky rings of tha in adducts with the DNA hexamer d(CGGCCG), since DNA is a potential target for this drug. Reactions of 1 with single-stranded d(CGGCCG) gave rise to ruthenation at each of the three G bases, whereas reactions of the duplex d(CGGCCG)2 with 1 mol equiv. 1 led to exclusive ruthenation of G3 and G6 (and G9, G12) and not G2 (or G8). Addition of a second mol equiv. of 1 gave di-ruthenated adducts (major sites G3/G6, G6/G9, G2/G6), and on reaction with a third mol equiv. tri-ruthenation (G2, G3/G6/G12).The NMR data are indicative of the coordinative binding of Ru-tha specifically to G3 and G6, together with penetrative intercalation of the bulky non-coordinated tha rings B and C of 1′, selectively between two base pairs G3/C10:C4/G9 and G6/C7:C5/G8. Intercalation at GpC base steps by tha has a lower energy penalty compared to intercalation at GpG base steps, thereby allowing accommodation of tha. Mono-intercalation of tha reduced the strength of H-bonding between en-NH and GO6. These differences in structural distortions compared to cisplatin induced by the coordinative binding of Ru-tha to GN7 may contribute to the differences in mechanism of action, including protein recognition of the metallated lesions, and lack of cross resistance.

Guanine bases in DNA are targets for some Ru–arene anticancer complexes. We have investigated the structure of the novel di-ruthenated d(GpG) adduct Ru2-GpG (where Ru = {(η6-biphenyl)-Ru(en)}2+ (1′)) in aqueous solution. 2D NMR results indicate that there are two conformers, supported by modeling studies. The major conformer I is a novel double-hamburger-like structure with a “head-to-head” (HH) base arrangement involving hydrophobic interactions between neighboring arene rings, the first example of a HH d(GpG) adduct constructed by weak interactions. Hence there are significant differences compared to Pt-d(GpG) adducts formed by cisplatin. There is no obviously rigid bending for the major conformer I. The minor conformer II of Ru2-GpG has a back-to-back structure, with two ruthenated guanine bases flipped away from each other. 19-23 base-pair oligodeoxyribonucleotides containing central TGGT sequences di-ruthenated by 1 show no directional bending, only slightly distorted di-ruthenated duplexes, consistent with the NMR data for conformer I. The structural differences and similarities of d(GpG) residues which are di-ruthenated or cross-linked by platination are discussed in the context of the biological activity of these metal complexes.

A nonporous neutral framework [CuCl2(m-bttmb)2]n (1) was changed into a porous ionic {[Cu(m-bttmb)2(H2O)Cl]Cl(CH3CN)0.5(H2O)2.75}n (2) by simply increasing the amount of CH3CN in the mixed solvent (CH3CN and H2O) or temperature in the reactions of CuCl2·2H2O with 1,3-bis(triazol-1-ylmethyl)-2,4,6-trimethylbenzene (m-bttmb). 1 undergoes transformation into 2 when treated with CH3CN. Both 1 and 2 have 2D 4-connected (4,4) network architectures but in different packing arrangements. These compounds have been characterized by single-crystal X-ray diffraction analysis, elemental analysis, IR spectra and thermogravimetric analysis. This work may provide a way to control the formation of neutral or ionic frameworks, as well as porosities by adjusting the polarity and components of the solvents.