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Synthesis of a series of two-dimensional metallamacrocycles via coordination-driven self-assembly of a shape-selective PtII2-molecular building unit incorporating carbazole-ethynyl functionality is described. An equimolar (1:1) combination of a Pt II2-organometallic 90° acceptor, 1, with rigid linear ditopic donors (La and Lb) afforded [4 + 4] self-assembled octanuclear molecular squares, 2 and 3, in quantitative yields, respectively [La = 4,4′-bipyridine; Lb = trans-1,2-bis(4-pyridyl) ethylene]. Conversely, a similar treatment of 1 with an amide-based unsymmetrical flexible ditopic donor, Lc, resulted in the formation of a [2 + 2] self-sorted molecular rhomboid (4a) as a single product [L c = N-(4-pyridyl)isonicotinamide]. Despite the possibility of several linkage isomeric macrocycles (rhomboid, triangle and square) due to the different connectivity of Lc, the formation of a single and symmetrical molecular rhomboid (4a) as the only product is an interesting observation. All the self-assembled macrocycles (2, 3 and 4a) were fully characterized by multinuclear NMR (1H and 31P) and ESI-MS analysis. Further structural insights about the size and shape of the macrocycles were obtained through energy minimization using density functional theory (DFT) calculations. Decoration of the starting carbazole building unit with Pt-ethynyl functionality enriches the assemblies to be more $\pi$-electron rich and luminescent in nature. Macrocycles 2 and 3 could sense the presence of electron deficient nitroaromatics in solution by quenching of the initial intensity upon gradual addition of picric acid (PA). They exhibited the largest quenching response with high selectivity for nitroaromatics compared to several other electron deficient aromatics tested. {\textcopyright} 2011 The Royal Society of Chemistry.

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Chemistry

(SoNS) School of Natural Sciences

Fulltext

Dalton Transactions

Coordination-driven self-assembly of 2D-metallamacrocycles using a shape-selective PtII2-organometallic 90° acceptor: Design, synthesis and sensing study

Highly luminescent micrometre-sized fine particles of a Zn(ii) metal-organic framework (MOF) of a new $\pi$-electron rich tricarboxylate dispersed in ethanol is demonstrated as a selective sensory material for the detection of nitroaromatic explosives via a fluorescence quenching mechanism. {\textcopyright} The Royal Society of Chemistry 2011.

Chemical Communications

Fluorescent metal-organic framework for selective sensing of nitroaromatic explosives

Four new neutral copper azido polymers, [Cu 4(N 3) 8(L 1)2] n (1), [Cu 4(N 3) 8(L 2)2] n (2), [Cu 4(N 3) 8(L 3)2] n (3) and [Cu9(N3)18(L 4)4]n (4) [L 1-4 are formed in situ by reacting pyridine-2-carboxaldehyde with 2-[2-(methylamino)ethyl]pyridine (mapy, L 1), N,N-dimethylethylenediamine (N,N-dmen, L 2), N,Ndiethylethylenediamine (N,N-deen, L 3) and N,N,2,2- tetramethylpropanediamine (N,N,2,2-tmpn, L 4)], have been synthesized by using 0.5 mol equiv of the chelating tridentate ligands with Cu- (NO 3) 2 33H 2O and an excess of NaN 3. Single-crystal X-ray structures show that the basic unit of these complexes, especially 1-3, contains very similar Cu II4 building blocks. The overall structure of 3 is two-dimensional, while the other three complexes are one-dimensional in nature.Complex 1 represents a unique example containing hemiaminal ether arrested by copper(II). Complexes 1 and 2 have a rare bridging azido pathway: both end-on and end-to-end bridging azides between a pair of Cu II centers. Cryomagnetic susceptibility measurements over a wide range of temperature exhibit dominant ferromagnetic behavior in all four complexes. Density functional theory calculations (B3LYP functional) have been performed on complexes 1-3 to provide a qualitative theoretical interpretation of their overall ferromagnetic behavior. {\textcopyright} 2011 American Chemical Society.

Inorganic Chemistry

Synthesis, structures and magnetic behavior of a series of copper(II) azide polymers of Cu 4 building clusters and isolation of a new hemiaminal ether as the metal complex

Three new transition metal complexes using 2-pyrimidineamidoxime (pmadH2) as multidentate chelating and/or bridging ligand have been synthesized and characterized. The ligand pmadH2 has two potential bridging functional groups [$\mu$-O and $\mu$-(N-O)] and consequently shows several coordination modes. While a polymeric 1D CuII complex [Cu(pmadH2)2(NO3)](NO3) (1) was obtained upon treatment of Cu(NO3)2{\textperiodcentered}3H2O with pmadH2 at room temperature in the absence of base, a high temperature reaction in the presence of base yielded a tetranuclear Cu II-complex [Cu4(pmad)2(pmadH) 2(NO3)](NO3)(H2O) (2). One of the CuII centers is in a square pyramidal environment while the other three are in a square planar geometry. Reaction of the same ligand with an equimolar mixture of both Cu(NO3)2{\textperiodcentered}3H2O and NiCl2{\textperiodcentered}6H2O yielded a tetranuclear heterometallic CuII2NiII2 complex [Cu2Ni2(pmad)2(pmadH)2Cl 2]{\textperiodcentered}H2O (3) containing both square planar (Ni II) and square pyramidal (CuII) metal centers. Complexes 1-3 represent the first examples of polynuclear metal complexes of 2-pyrimidineamidoxime. The analysis of variable temperature magnetic susceptibility data of 2 reveals that both ferromagnetic and antiferromagnetic interactions exist in this complex (J1 = +10.7 cm-1 and J2 = -2.7 cm-1 with g = 2.1) leading to a resultant ferromagnetic behavior. Complex 3 shows expected antiferromagnetic interaction between two CuII centers through -N-O- bridging pathway with J 1 = -3.4 cm-1 and g = 2.08. DFT calculations have been used to corroborate the magnetic results. {\textcopyright} 2010 The Royal Society of Chemistry.

Use of 2-pyrimidineamidoxime to generate polynuclear homo-/heterometallic assemblies: Synthesis, crystal structures and magnetic study with theoretical investigations on the exchange mechanism

Reaction of formamide with Ni(NO3)2{\textperiodcentered}6H 2O under hydrothermal condition in a mixture of MeOH/H2O forms a two-dimensional formate bridged sheet Ni(HCOO)2(MeOH) 2 (1). X-ray structure analysis reveals the conversion of formamide to formate which acts as a bridging ligand in complex 1 where the axial sites of Ni(II) are occupied by methanol used as a solvent. An analogous reaction in presence of 4,4′-bipyridyl (4,4′-bipy) yielded a three-dimensional structure Ni(HCOO)2(4,4′-bpy) (2). DC magnetic measurements as a function of temperature and field established the presence of spontaneous magnetization with Tc (Curie temperature) = 17 and 20.8 K in 1 and 2, respectively, which can be attributed due to spin-canting. DFT calculations were performed to corroborate the magnetic results of 1 and 2. {\textcopyright} 2010 Elsevier Ltd. All rights reserved.

Polyhedron

A formate bridged Ni(II) sheet and its 3D analogue in presence of a linear organic linker: Synthesis, crystal structure and magnetic properties

The crystal structures and magnetic properties of five new transition metal-azido complexes with two anionic [pyrazine-2-carboxylate (pyzc) and p-aminobenzoate (paba)] and two neutral [pyrazine (pyz) and pyridine (py)] coligands are reported. All five complexes were synthesized by solvothermal methods. The complex [Co2(pyzc)2(N3) 2(H2O)2]n (1) is 1D and exhibit canted antiferromagnetism, while the 3D complex [MnNa(pyzc)(N3) 2(H2O)2]n (2) has a complicated structure and is weakly ferromagnetic in nature. [Mn2(paba) 2(N3)2(H2O)2] n (3), is a 2D sheet and the MnII ions are found to be antiferromagnetically coupled. The isostructural 2D complexes [Cu 3(pyz)2(N3)6]n (4) and [Cu3(py)2(N3)6]n (5) resemble remarkably in their magnetic properties exhibiting moderately strong ferromagnetism. Density functional theory calculations (B3LYP functional) have been performed to provide a qualitative theoretical interpretation of the overall magnetic behavior shown by these complexes. {\textcopyright} 2010 The Royal Society of Chemistry.

A series of transition metal-azido extended complexes with various anionic and neutral co-ligands: Synthesis, structure and their distinct magnetic behavior

Research on structure and magnetic properties of polynuclear metal complexes to understand the structural and chemical factors governing the electronic exchange coupling mediated by multi-atom bridging ligands is of growing interest. Hydrothermal treatment of Ni(NO3) 2{\textperiodcentered}6H2O with N-(4-carboxyphenyl)iminodiacetic acid [N-4(H3CPIDA)] at 150 °C yielded a 3D coordination polymer of general formula [Ni3{N-4(CPIDA)}2(H2O) 3]{\textperiodcentered}6H2O (1). An analogous network of general formula [Co3{N-3(CPIDA)}2(H2O) 3]{\textperiodcentered}3H2O (2) was synthesized using N-(3-carboxyphenyl)iminodiacetic acid [N-3(H3CPIDA)] in combination with Co(NO3)2{\textperiodcentered}6H2O under identical reaction condition. Both the complexes contain trinuclear secondary building unit and crystallized in monoclinic system with space groups C2/c (1) and P21/c (2), respectively. Variable temperature magnetic characterization of these complexes in the temperature range of 2-300 K indicated the presence of overall ferromagnetic and antiferromagnetic behavior for 1 and 2, respectively. Density functional theory calculations (B3LYP functional) were performed for further insight on the trinuclear units to provide a qualitative theoretical interpretation on the overall magnetic behavior of the complexes 1 and 2. {\textcopyright} 2010 Elsevier B.V. All rights reserved.

Inorganica Chimica Acta

Synthesis, crystal structures and magnetic behavior of two 3D coordination polymers using N-(4/3-carboxyphenyl)iminodiacetic acids as bridging ligands

Two components self-assembly of a Pd4 neutral molecular rectangle driven by Pd–O bond coordination has been achieved and this $\Pi$-electron rich rectangle shows fluorescence quenching in presence of nitroaromatics, which are the chemical signatures of many explosives. {\textcopyright} 2009 The Royal Society of Chemistry.

Journal of the Chemical Society. Dalton Transactions

Self-assembly of a PdII neutral molecular rectangle via a new organometallic PdII2 molecular clip and oxygen donor linker

The design and two-component [2 + 3] self-assembly of a series of new organometallic molecular prisms (3a-d) are described. Assemblies 3a,b incorporate 4,4',4'-tris[ethynyl-trans-Pt(PEt2)2(N0 3)]triphenylamine (la) containing a Pt-ethynyl functionality as tritopic planar acceptor and organic "clips" 2a and 2b, respectively [where 2a = l,3-bis(3-pyridyl)isophthalic amide; 2b = l,3-bis(ethynyl3-pyridyl) benzene]. In a complementary approach an organic tritopic planar donor ligand 2c [2c = 4,4',4'-tris(4-pyridylethynyl)triphenylamine] was assembled with an organometallic "clip", 1,8-bis[{trans-Pt(PEt3) 2(N03)}ethynyl]anthracene (lb), to obtain prism 3c. A new organometallic carboncentered acceptor, l,l,l-tris[4-{trans-Pt(PEt 3)2(N03)}ethynylphenyl]ethane (1c), has been prepared and its prism derivative (3d) using an organic "clip" is prepared. Assemblies (3a-d) were characterized by multinuclear NMR spectroscopy, electrospray ionization mass spectroscopy and elemental analysis. 3a-d showed fluorescence behavior in solution and quenching of fluorescence intensity (3a, 3c-d) was noticed upon addition of TNT (2,4,6-trinitrotoluene), a common constituent of many commercial explosives. A thin film of the assembly 3d made by spin coating of a solution of 3x 10-5 M in DMF on a 1 cm 2 quartz plate showed fluorescence response to the vapor of TNT. Copy; 2009 American Chemical Society.

Organometallics

Self-Assembly of molecular prisms via Pt3 organometallic acceptors and a Pt2 organometallic clip

Two new neutral copper-azido polymers [Cu3(N3) 6(tmen)2]n (1) and [Cu6(N 3)12(deen)2]n (2) [tmen = N,N,N,N -tetramethylethylenediamine and deen = N,N-diethylethylenediamine] have been synthesized by using lower molar equivalents of the chelating diamine ligands with Cu(NO3)2 {\textperiodcentered} 3H2O and an excess of NaN3. The single crystal X-ray structure shows that in the basic unit of the 1D complex 1, the three Cu" ions are linked by double end-on azido bridges with CU-NEO-CU angles on both sides of the magnetic exchange critical angle of 108°. Complex 2 is a 3D framework of a basic Cu6 cluster. Cryomagnetic susceptibility measurements over a wide range of temperature exhibit dominant ferromagnetic behavior in both the complexes. Density functional theory calculations (B3LYP functional) have been performed on the trinuclear unit to provide a qualitative theoretical interpretation of the overall ferromagnetic behavior shown by the complex 1. {\textcopyright}2009 American Chemical Society.