Copper(i)-iodide cluster structures as functional and processable platform materials.

The combination of the copper(i)-iodide entity with organic ligands gives rise to a large variety of CuII polynuclear structures in the form of molecular complexes or extended structures. An appropriate selection of these components allows the preparation of materials showing interesting physicochemical properties and potential applications, mainly focused on organic light-emitting diodes and optical sensors. The most prominent physical feature of these materials is their emission, which can be modulated using the chemical structure and composition. This review article collates the advances in this research field, rationalizing the information into two main blocks as a function of the dimensionality of the structures: molecular complexes and extended networks. We describe the most typical ways of preparation, structures, and properties, with particular attention to the processability of the material as a fundamental aspect of the integration of the materials into real devices. Therefore, we aim to integrate the basic elements of the coordination chemistry of CuII clusters from the materials science perspective to envision this promising research field's potential technological future.

Cu(I)-I-2,4-diaminopyrimidine Coordination Polymers with Optoelectronic Properties as a Proof of Concept for Solar Cells.

Two coordination polymers with formulas [CuI(dapym)]n and [Cu2I2(dapym)]n (dapym = 2,4-diaminopyrimidine) have been synthesized in water at room temperature. According to the stoichiometry used, mono (1D) and the two-dimensional (2D) structures can be obtained. Both are made up of Cu2I2 double chains. Their high insolubility in the reaction medium also makes it possible to obtain them on a nanometric scale. Their structural flexibility and short Cu-Cu distances provoke interesting optoelectronic properties and respond to physical stimuli such as pressure and temperature, making them interesting for sensor applications. The experimental and theoretical studies allow us to propose different emission mechanisms with different behaviors despite containing the same organic ligand. These behaviors are attributed to their structural differences. The emission spectra versus pressure and temperature suggest competencies between different transitions, founding critical Cu2I2 environments, i.e., symmetric in the 1D compound and asymmetric for the 2D one. The intensity in the 2D compound's emission increases with decreasing temperature, and this behavior can be rationalized with a structural constriction that decreases the Cu-Cu and Cu-I distances. However, compound 1D exhibits a contrary behavior that may be related to a change of the organic ligand's molecular configuration. These changes imply that a more significant Π-Π interaction counteracts the contraction in distances and angles when the temperature decreased. Also, the experimental conductivity measurements and theoretical calculations show a semiconductor behavior. The absorption of the 1D compound in UV, its intense emission at room temperature, and the reduction to nanometric size have allowed us to combine it homogeneously with ethyl vinyl acetate (EVA), creating a new composite material. The external quantum efficiency of this material in a Si photovoltaic mini-module has shown that this compound is an active species with application in solar cells since it can move the photons of the incident radiation (UV region) to longer wavelengths.

Multifunctional Copper(I) Coordination Polymers with Aromatic Mono- and Ditopic Thioamides.

Direct reactions under ambient conditions between CuX (X = Br, I) and thiobenzamide (TBA) were carried out at different ratios, giving rise to the formation of a series of one-dimensional (1D) coordination polymers, (CPs) [CuI(TBA)] n (1), [Cu3I3(TBA)2] n (4), and [CuBr(TBA)] n (5), as well as two molecular complexes, [CuI(TBA)3] (2) and [Cu2I2(TBA)4]·2MeCN (3). Recrystallization of 1 and 5 yielded a series of isostructural 1D CP solvated species, [CuI(TBA)·S] n] n (1·S; S = tetrahydrofuran, acetone, methanol) and [CuBr(TBA)·S] n (5·S; S = tetrahydrofuran, acetone), respectively. Similar reactions between CuI and 1,4-dithiobenzamide (DTBA) allowed the isolation of a series of two-dimensional (2D) CPs [CuI(DTBA)·S] n (6·S; S = N, N-dimethylformamide, acetonitrile, methanol). Interestingly, 1·S and 5·S showed variable luminescence and electrical semiconductivity depending on the different solvents located in their structures. Thus, 1 and 5 could display potential application for sensing volatile organic vapors by virtue of the significant changes in their emission upon solvent exposure, even by the naked eye. Theoretical calculations have been used to rationalize these electronic properties.

Luminescent Thermochromism of 2D Coordination Polymers Based on Copper(I) Halides with 4-Hydroxythiophenol.

Solvothermal reactions between copper(I) halides and 4-mercaptophenol give rise to the formation of three coordination polymers with general formula [Cu3 X(HT)2 ]n (X=Cl, 1; Br, 2; and I, 3). The structures of these coordination polymers have been determined by X-ray diffraction at both room- and low temperature (110 K), showing a general shortening in Cu-S, Cu-X and Cu-Cu bond lengths at low temperatures. 1 and 2 are isostructural, consisting of layers in which the halogen ligands act as µ3 -bridges joining two Cu1 and one Cu2 atoms whereas in 3 the iodine ligands is as µ4 -mode but the layers are quasi-isostructural with 1 or 2. These compounds show a reversible thermochromic luminescence, with strong orange emission for 1 and 2, but weaker for 3 at room temperature, whereas upon cooling at 77 K 1 and 2 show stronger yellow emission, and 3 displays stronger green emission. DFT calculations have been used to rationalize these observations. These results suggest a high potential for this novel and promising stimuli-responsive materials.

Electrical Conductivity and Strong Luminescence in Copper Iodide Double Chains with Isonicotinato Derivatives.

Direct reactions between CuI and isonicotinic acid (HIN) or the corresponding esters, ethyl isonicotinate (EtIN) or methyl isonicotinate (MeIN), give rise to the formation of the coordination polymers [CuI(L)]n with L=EtIN (1), MeIN (2) and HIN (3). Polymers 1-3 show similar structures based on a CuI double chain in which ethyl-, methyl isonicotinate or isonicotinic acid are coordinated as terminal ligands. Albeit, their supramolecular architecture differs considerably, affecting the distances and angles of the central CuI double chains and thereby their physical properties. Hence, the photoluminescence shows remarkable differences; 1 and 2 show a strong yellow emission, whereas 3 displays a weak emission; and 1 and 2 are semiconductors with moderate room temperature conductivities, whereas 3 has increased electrical conductivity up to 3×10(-3)  S cm(-1) . Additionally, 1 and 2 present an irreversible transition to a highly conducting phase with a conductivity almost 4 orders of magnitude higher and a quasi-metallic behaviour. Thermogravimetric analysis (TGA) coupled to a mass spectrometer and magnetic measurements point to a partial thermally induced oxidation of the carboxylate groups of the ligands with Cu(I) to Cu(0) reduction. DFT calculations have been carried out to rationalise these observations.

Electrical conductivity and luminescence in coordination polymers based on copper(I)-halides and sulfur-pyrimidine ligands.

The solvothermal reactions between pyrimidinedisulfide (pym(2)S(2)) and CuI or CuBr(2) in CH(2)Cl(2):CH(3)CN lead to the formation of [Cu(11)I(7)(pymS)(4)](n) (pymSH = pyrimidine-2(1H)-thione) (1) and the dimer [Cu(II)(µ-Br)(Br)L](2) (L = 2-(pyrimidin-2-ylamino)-1,3-thiazole-4-carbaldehyde) (2). In the later reaction, there is an in situ S-S, S-C(sp(2)), and C(sp(2))-N multiple bond cleavage of the pyrimidinedisulfide resulting in the formation of 2-(pyrimidin-2-ylamino)-1,3-thiazole-4-carbaldehyde. Interestingly, similar reactions carried out just with a change in the solvent (H(2)O:CH(3)CN instead of CH(2)Cl(2):CH(3)CN) give rise to the formation of coordination polymers with rather different architectures. Thus, the reaction between pym(2)S(2) and CuI leads to the formation of [Cu(3)I(pymS)(2)](n) (3) and [CuI(pym(2)S(3))] (pym(2)S(3) = pyrimidiltrisulfide) (4), while [Cu(3)Br(pymS)(2)](n) (5) is isolated in the reaction with CuBr(2). Finally, the solvothermal reactions between CuI and pyrimidine-2-thione (pymSH) in CH(2)Cl(2):CH(3)CN at different ratios, 1:1 or 2:1, give the polymers [Cu(2)I(2)(pymSH)(2)](n) (6) and [Cu(2)I(2)(pymSH)](n) (7), respectively. The structure of the new compounds has been determined by X-ray diffraction. The studies of the physical properties of the novel coordination polymers reveal that compounds 3 and 5 present excellent electrical conductivity values at room temperature, while compounds 1, 3, and 5-7 show luminescent strong red emission at room temperature.

Structure and properties of one-dimensional heterobimetallic polymers containing dicyanoaurate and dirhodium(II) fragments.

The synthesis and characterization of compound [Rh(2)(O(2)CEt)(4)(H(2)O)(2)] (1) and one-dimensional heterobimetallic polymers K(n){Rh(2)(O(2)CEt)(4)[Au(CN)(2)]}(n) (2) and K(n){Rh(2)(O(2)CMe)(4)[Au(CN)(2)]}(n)·4nH(2)O (3), constructed from dirhodiumtetracarboxylato units, [Rh(2)(O(2)CR)(4)](+), and dicyanoaurate, [Au(CN)(2)](-), fragments are described. In both compounds 2 and 3 the resulting polymeric chains are nonlinear and have in common similar structural parameters, although the solid state supramolecular arrangement is very different. These structural differences explain the fact that complex 2 displays aurophilic interactions while this type of interactions are absent in complex 3. As a result, compound 2 shows rich blue luminescent properties whereas compound 3 is not luminescent. The electrical conductivity in solid state of compounds 2 and 3 is also studied.

A conducting coordination polymer based on assembled Cu9 cages.

We report on a novel highly semiconducting 1D coordination polymer architecture obtained by the reaction of a Cu(II) salt with 2,2'-dipyridyldisulfide under microwave solvothermal conditions. This reaction proceeds with an unusual C-S and S-S bond cleavage of the 2,2'-dipyridyldisulfide ligand. The unprecedented architecture of this coordination polymer consists of a 1D chain formed by the assembling of Cu9 cluster cages. The electrical conductivity behavior of this novel material suggests new perspectives for the use of coordination polymers as electrical conducting materials.

One-Pot Preparation of Mechanically Robust, Transparent, Highly Conductive, and Memristive Metal-Organic Ultrathin Film.

The future of 2D flexible electronics relies on the preparation of conducting ultrathin films of materials with mechanical robustness and flexibility in a simple but controlled manner. In this respect, metal-organic compounds present advantages over inorganic laminar crystals owing to their structural, chemical, and functional diversity. While most metal-organic compounds are usually prepared in bulk, recent work has shown that some of them are processable down to low dimensional forms. Here we report the one-pot preparation, carried out at the water-air interface, of ultrathin (down to 4 nm) films of the metal-organic compound [Cu2I2(TAA)] n (TAA= thioacetamide). The films are shown to be homogeneous over mm2 areas, smooth, highly transparent, mechanically robust, and good electrical conductors with memristive behavior at low frequencies. This combination of properties, as well as the industrial availability of the two building blocks required for the preparation, demonstrates their wide range potential in future flexible and transparent electronics.

Smart composite films of nanometric thickness based on copper-iodine coordination polymers. Toward sensors.

One-pot reactions between CuI and methyl or methyl 2-amino-isonicotinate give rise to the formation of two coordination polymers (CPs) based on double zig-zag Cu2I2 chains. The presence of a NH2 group in the isonicotinate ligand produces different supramolecular interactions affecting the Cu-Cu distances and symmetry of the Cu2I2 chains. These structural variations significantly modulate their physical properties. Thus, both CPs are semiconductors and also show reversible thermo/mechanoluminescence. X-ray diffraction studies carried out under different temperature and pressure conditions in combination with theoretical calculations have been used to rationalize the multi-stimuli-responsive properties. Importantly, a bottom-up procedure based on fast precipitation leads to nanofibers of both CPs. The dimensions of these nanofibres enable the preparation of thermo/mechanochromic film composites with polyvinylidene difluoride. These films are tens of nanometers in thickness while being centimeters in length, representing smaller thicknesses so far reported for thin-film composites. This nanomaterial integration of CPs could represent a source of alternative nanomaterials for opto-electronic device fabrication.

On-surface self-organization of a robust metal-organic cluster based on copper(I) with chloride and organosulphur ligands.

Direct sublimation of a Cu4Cl4 metal-organic cluster on Cu(110) under ultra-high vacuum allows the formation of ultra-large well-organized metal-organic supramolecular wires. Our results show that the large monomers assemble with each other by π-π interactions connecting dipyrimidine units and are stabilized by the surface.

Solvent-induced delamination of a multifunctional two dimensional coordination polymer.

A coordination polymer is fully exfoliated by solvent-assisted interaction only. The soft-delamination process results from the structure of the starting material, which shows a layered structure with weak layer-to-layer interactions and cavities with the ability to locate several solvents in an unselective way. These results represent a significant step forward towards the production of structurally designed one-molecule thick 2D materials with tailored physico-chemical properties.

Unexpected multiple bond cleavage and rearrangement of organosulfide ligands in the presence of Cu(II) assisted by solvothermal and solvothermal-microwave conditions.

An unprecedented in situ multiple bond cleavage of S-S, S-C(sp(2)) and C-N in the pyrimidinedisulfide (pym(2)S(2)) ligand is observed by the reaction of CuCl(2)·2H(2)O with this ligand under solvothermal and solvothermal-microwave conditions. In this process the formation of the compound [Cu(II)(µ-Cl)(Cl)L](2), where L represents the new ligand (L = 2-(pyrimidin-2-ylamino)-1,3-thiazole-4-carbaldehyde), is observed. This ligand has been further isolated and X-ray characterized. The similar reaction carried out under solvothermal-microwave conditions gives, in addition to the latter compound, the complex {9·[Cu(pym(2)S(3))(µ-Cl)(Cl)](2)·[Cu(pym(2)S(2))(µ-Cl)(Cl)](2)}. Coordination of a pyrimidinetrisulfide ligand (pym(2)S(3)) is reported for the first time. This work represents an illustrative example of the novel synthetic perspectives attainable via solvothermal-microwave procedures.

Dynamic combinatorial chemistry in a solvothermal process of Cu(I,II) and organosulfur ligands.

An unprecedented microwave C(sp(2))-S and S-S bond activation of 2,2'-dipyridyldisulfide (2-dpds) and the formation of a new architecture of coordination networks obtained by reaction of Cu(HCO(2))(2).xH(2)O with 2-dpds under solvothermal microwave conditions are reported. This unusual reaction proceeds with the partial oxidation of 2,2'-dipyridyldisulfide to sulfate. The process generates: a Cu(I) dimetallic complex [Cu(2)(mu-Hpyt)(2)(Hpyt)(4)](SO(4)).approximately 5EtOH (1), a Cu(I,II) polycationic coordination polymer [Cu(H(2)O)(6)][Cu(6)(mu-Hpyt)(12)](SO(4))(4).4H(2)O (2) and a dimetallic Cu(II) complex [Cu(2-dps)(mu-SO(4))(H(2)O)](2).3H(2)O (3). It is worth mentioning the strong red luminescence shown by compounds 1 and 2.

Single layers of a multifunctional laminar Cu(I,II) coordination polymer.

A multifunctional bidimensional mixed-valence copper coordination polymer [Cu2Br(IN)2]n (IN = isonicotinato) has been characterized in crystal phase and isolated on graphite surface as single sheets.

Electronic communication through a poly-yne carbonyldicobalt complex containing an open linear triosmium cluster.

The oxidative coupling of 2-[Co(2)(CO)(4)(micro-X){micro(2)-eta(2)-(SiMe(3)C(2))}]-5-(C[triple bond]CH)C(4)H(2)S (X = dppa (1), dppm (2)) and 3-[Co(2)(CO)(4)(micro-dmpm){micro(2)-eta(2)-(SiMe(3)C(2))}]-4-(C[triple bond]CH)C(4)H(2)S (3) using standard Eglinton-Glaser conditions yielded 2,2'-[Co(2)(CO)(4)(micro-X){micro(2)-eta(2)-(SiMe(3)C(2))}C(4)H(2)S](2)-5,5'-(C[triple bond]C)(2) (X = dppa (4), dppm (5)) and 3,3'-[Co(2)(CO)(4)(micro-dmpm){micro(2)-eta(2)-(SiMe(3)C(2))}C(4)H(2)S](2)-4,4'-(C[triple bond]C)(2) (6), respectively (dppa = (Ph(2)P)(2)NH; dmpm = (Me(2)P)(2)CH(2); dppm = (Ph(2)P)(2)CH(2)). The reaction of 5 with [Os(3)(CO)(11)(CH(3)CN)] afforded 2,2'-[Co(2)(CO)(4)(micro-dppm){micro(2)-eta(2)-(SiMe(3)C(2))}C(4)H(2)S](2)-5,5'-[Os(3)(CO)(11)(micro(3)-eta(4)-(C[triple bond]C)(2)] (7), where the triosmium cluster is open and coordinated as a linear chain to both triple bonds. The electrochemical study of 7 shows that the "Os(3)" unit significantly enhances the electronic communication between the "Co(2)" redox centres as compared with 5. Complex 6 was characterized by single-crystal X-ray diffraction analyses.