Template–Framework Interactions in Tetraethylammonium‐Directed Zeolite Synthesis

Zeolites, having widespread applications in chemical industries, are often synthesized using organic templates. These can be cost‐prohibitive, motivating investigations into their role in promoting crystallization. Herein, the relationship between framework structure, chemical composition, synthesis conditions and the conformation of the occluded, economical template tetraethylammonium (TEA⁺) has been systematically examined by experimental and computational means. The results show two distinct regimes of occluded conformer tendencies: 1) In frameworks with a large stabilization energy difference, only a single conformer was found (BEA, LTA and MFI). 2) In the frameworks with small stabilization energy differences (AEI, AFI, CHA and MOR), less than the interconversion of TEA⁺ in solution, a heteroatom‐dependent (Al, B, Co, Mn, Ti, Zn) distribution of conformers was observed. These findings demonstrate that host–guest chemistry principles, including electrostatic interactions and coordination chemistry, are as important as ideal pore‐filling.     

Modulation of the Physicochemical Properties of Donor–Spiro–Acceptor Derivatives through Donor Unit Planarisation: Phenylacridine versus Indoloacridine—New Hosts for Green and Blue Phosphorescent Organic Light‐Emitting Diodes (PhOLEDs)

This work reports a detailed structure–property relationship study of a series of efficient host materials based on the donor–spiro–acceptor (D‐spiro‐A) design for green and sky‐blue phosphorescent organic light‐emitting diodes (PhOLEDs). The electronic and physical effects of the indoloacridine (IA) fragment connected through a spiro bridge to different acceptor units, namely, fluorene, dioxothioxanthene or diazafluorene moiety, have been investigated in depth. The resulting host materials have been easily synthesised through short, efficient, low‐cost, and highly adaptable synthetic routes by using common intermediates. The dyes possess a very high triplet energy (E_T) and tuneable HOMO/LUMO levels, depending on the strength of the donor/acceptor combination. The peculiar electrochemical and optical properties of the IA moiety have been investigated though a fine comparison with their phenylacridine counterparts to study the influence of planarisation. Finally, these molecules have been incorporated as hosts in green and sky‐blue PhOLEDs. For the derivative SIA‐TXO₂ as a host, external quantum efficiencies as high as 23 and 14 % have been obtained for green and sky‐blue PhOLEDs, respectively.     

Host–Guest Chemistry between Perylene Diimide (PDI) Derivatives and 18‐Crown‐6: Enhancement in Luminescence Quantum Yield and Electrical Conductivity

Perylene diimide (PDI) derivatives exhibit a high propensity for aggregation, which causes the aggregation‐induced quenching of emission from the system. Host–guest chemistry is one of the best‐known methods for preventing aggregation through the encapsulation of guest molecules. Herein we report the use of 18‐crown‐6 (18‐C‐6) as a host system to disaggregate suitably substituted PDI derivatives in methanol. 18‐C‐6 formed complexes with amino‐substituted PDIs in methanol, which led to disaggregation and enhanced emission from the systems. Furthermore, the embedding of the PDI ? 18‐C‐6 complexes in poly(vinyl alcohol) (PVA) films generated remarkably high emission quantum yields (60–70 %) from the PDI derivatives. More importantly, the host–guest systems were tested for their ability to conduct electricity in PVA films. The electrical conductivities of the self‐assembled systems in PVA were measured by electrochemical impedance spectroscopy (EIS) and the highest conductivity observed was 2.42×10^?5 S cm^?1.     

Interpenetrated Cage Structures

This Review covers design strategies, synthetic challenges, host–guest chemistry, and functional properties of interlocked supramolecular cages. Some dynamic covalent organic structures are discussed, as are selected examples of interpenetration in metal–organic frameworks, but the main focus is on discrete coordination architectures, that is, metal‐mediated dimers. Factors leading to interpenetration, such as geometry, flexibility and chemical makeup of the ligands, coordination environment, solvent effects, and selection of suitable counter anions and guest molecules, are discussed. In particular, banana‐shaped bis‐pyridyl ligands together with square‐planar metal cations have proven to be suitable building blocks for the construction of interpenetrated double‐cages obeying the formula [M₄L₈]. The peculiar topology of these double‐cages results in a linear arrangement of three mechanically coupled pockets. This allows for the implementation of interesting guest encapsulation effects such as allosteric binding and template‐controlled selectivity. In stimuli‐responsive systems, anionic triggers can toggle the binding of neutral guests or even induce complete structural conversions. The increasing structural and functional complexity in this class of self‐assembled hosts promises the construction of intelligent receptors, novel catalytic systems, and functional materials.     

Molecular distortion effect on ff-emission in a Pr(III) complex with 4,7-diphenyl-1,10-phenanthroline.

The electronic and structural behaviour of a Pr(III) complex with 4,7-diphenyl-1,10-phenanthroline, [Pr(bathophen)(2)(NO(3))(3)], is investigated with respect to the effect of configuration changes on the Pr(III) centre. [Pr(bathophen)(2)(NO(3))(3)] luminesces from the excited states of the ligand and the metal ion. The fluorescence, ff-emission ((1)D(2)-->(3)H(4)), and phosphorescence bands appear at 394, 608.2 and 482 nm, respectively, in the solid state. In acetonitrile, the complex also shows multiple emissions. From the time-resolved emission and the lifetime measurements, the excitation energy-transfer in [Pr(bathophen)(2)(NO(3))(3)] is clarified, that is, the upper excited triplet level of the ligand acts as an energy donor, while the (1)D(2) levels of Pr(III) is the acceptor. Additionally, the emission phenomena of the complex can be modified by molecular distortion, particularly by rotation of the phenyl groups in the ligand.     

Thermodynamics of the decomposition processes of donor-acceptor complexes MX3 x en x MX3 and MX3 x en.

The structural and thermodynamic properties of the donor-acceptor (DA) complexes of Group 13 metal halides (MX3) with ethylenediamine and their decomposition products have been studied theoretically at the B3LYP/LANL2DZ(d,p) level of theory. Gas-phase dissociation into various components and HX elimination reactions are considered. Both processes are endothermic but favored by entropy. Complexes of 2:1 composition are predicted to be stable in the gas phase up to 640-1000 K. It is found that complexation with the second acceptor molecule lowers the HX elimination enthalpy; in turn, HX elimination increases DA bonding with a second MX3 molecule. Exceptionally high values of the dissociation enthalpies (310-390 kJ mol(-1)) and HX elimination reactions (360-420 kJ mol(-1)) of the amido compounds MX2NHC2H4NH2 and MX2NHC2H4NHMX2 make them important intermediates in the decomposition processes. Dissociation reactions of the complexes are more favorable than HX elimination reactions; however, the subsequent oligomerization and cyclization processes of coordinationally unsaturated amido and imido compounds may facilitate HX elimination. Since HI elimination reactions are predicted to be the least endothermic, and aluminum-containing compounds have the strongest M-N dissociation enthalpies, it is expected that compounds based on aluminum iodide are promising objects for experimental studies.     

Supramolecular assemblies of sulfonatocalixarenes with phenanthroline: factors governing capsule formation versus bilayer arrangements

Four crystalline complexes were prepared by the inclusion complexation of the 1,10-phenanthrolinium ion (Phen) with p-sulfonatothiacalix[4]arene (TCAS) (2 from a solution at pH 1-2 and 4 from 1 M HCl) and with p-sulfonatocalix[5]arene (C5AS) (3 from a solution at pH 1-2 and 5 from 1 M HCl) upon varying the acidity of the solution. By combining the results obtained for complexes 2-5 with those for our previously reported complex (1), p-sulfonatocalix[4]arene (C4AS) complexed to Phen, it was revealed that p-sulfonatocalixarenes (CASs) form "bis-molecular" capsules (1, 2, and 3) around Phen at pH 1-2, whereas complexes 4 and 5 display distinct host-guest inclusion behavior at higher acid concentrations. The degree of compactness of the capsules increases with the enlargement of the calixarene cavity, which is affected significantly by both the penetration depth of Phen and the structure of the Phen dimer. Furthermore, the complexation behavior of TCAS/C5AS with Phen in 1 M DCl was investigated by using NMR spectroscopy, and was discussed in comparison with the previously reported results obtained from solutions at pH 2.0.     

Donor/conductor/acceptor triads spatially organized on the micrometer-length scale: an alternative approach to photovoltaic cells

We have used porous anodised Al(2)O(3) membranes as inert matrix for constructing and organizing spatially ternary donor/conductor/acceptor (DCA) systems exhibiting photovoltaic cell activity on the micrometric-length scale. These DCA triads were built stepwise by first growing a conducting polymer inside the membrane pores, thus forming nanorods that completely fill the internal pore space of the membrane. Then, an electron donor and an electron acceptor were adsorbed one on each side of the membrane, so that they were separated by a distance equal to the membrane thickness (ca. 60 microm), but electronically connected through the conductive polymer. When this device was placed between two electrodes and irradiated with visible light, electrons jumped from the donor molecule, crossed the membrane from side to side through the conductive polymer (a journey of about 60 microm!) until they finally reach the acceptor molecule. In so doing, an electric voltage was generated between the two electrodes, capable of maintaining an electric current flow from the membrane to an external circuit. Our DCA device constitutes the proof of a novel concept of photovoltaic cells, since it is based on the spatial organization at the micrometric scale of complementary, but not covalently linked, electron-donor and electron-acceptor organic species. Thus, our cell is based in translating photoinduced electron transfer between donors and acceptors, which is known to occur at the molecular nanometric scale, to the micrometric range in a spatially organised system. In addition our cell does not need the use of liquid electrolytes in order to operate, which is one of the main drawbacks in dye-sensitised solar cells.     

Stereoselective preparation of six diastereomeric quatercyclopropanes from bicyclopropylidene and some derivatives

Diastereomeric meso- and d,l-bis(bicyclopropylidenyl) (5) were obtained upon oxidation with oxygen of a higher-order cuprate generated from lithiobicyclopropylidene (4) in 50 and 31 % yield, respectively. Their perdeuterated analogues meso-[D(14)]- and d,l-[D(14)]-5 were obtained along the same route from perdeuterated bicyclopropylidene [D(8)]-3 (synthesized in six steps in 7.4 % overall yield from [D(8)]-THF) in 20.5 % yield each. Dehalogenative coupling of 1,1-dibromo-2-cyclopropylcyclopropane (6) gave a mixture of all possible stereoisomers of 1,5-dicyclopropylbicyclopropylidene 16 in 69 % yield, from which (Z)-cis-16 was separated by preparative gas chromatography (26 % yield). The crystal structure of meso-5 looks like a superposition of the crystal structures of two outer bicyclopropylidene units (3) and one inner s-trans-bicyclopropyl unit, whereas the two outer cyclopropyl moieties adopt a gauche orientation with respect to the cyclopropane rings at the inner bicyclopropylidene units in (Z)-cis-16. Birch reduction with lithium in liquid ammonia of meso-5 and d,l-5 gave two pairs of diastereomeric quatercyclopropanes trans,trans-(R*,S*,R*, S*)-17/cis,trans-(R*,S*,R*,R*)-18 and trans,trans-(R*,S*,S*,R*)-19/cis,trans-(R*,S*,S*,S*)-20 in 97 and 76 % yield, respectively, in a ratio 9:1 for every pair. The latter diastereomer was also obtained as the sole product by Birch reduction of (Z)-cis-16 in 96 % yield. Under the same conditions, tetradecadeuterio analogues trans,trans-[D(14)]-(R*,S*,R*,S*)-17/cis,trans-[D(14)]-(R*, S*,R*,R*)-18 (8:1) and trans,trans-[D(14)]-(R*,S*,S*,R*)-19/cis,trans-[D(14)]-(R*,S*,S*,S*)-20 (12:1) were prepared from meso-[D(14)]-5 and d,l-[D(14)]-5 in 37 and 63 % yield, respectively. Reduction of meso-5 with diimine gave the cis,cis-quatercyclopropane (S*,S*,R*,R*)-21 as the main product (58 % yield) along with the cis,trans-diastereomer (S*,S*,R*,S*)-18 (29 % yield). Thus, five of the six possible diastereomeric quatercyclopropanes were obtained from meso-5, d,l-5, and (Z)-cis-16. The X-ray crystal structure analyses of trans,trans-(R*,S*,R*,S*)-17 and cis,cis-(S*,S*,R*,R*)-21 revealed for the both an unusual conformation in which the central bicyclopropyl unit adopts an s-trans-(antiperiplanar) orientation with phi=180.0 degrees , and the two terminal bicyclopropyl moieties adopt a synclinal conformation with phi=49.8 and 72.0 degrees , respectively. In solution the vicinal coupling constants (3)J(H,H) in trans,trans-(R*,S*,R*,S*)-[D(14)]-17, trans,trans-(R*,S*,S*,R*)-[D(14)]-19, trans,cis-(R*,S*,R*,R*)-[D(14)]-18 and trans,cis-(R*,S*,S*,S*)-[D(14)]-20 were found to be 4.1, 4.7, 5.9 and 5.9 Hz, respectively. This indicates a predominance of the all-gauche conformer in (R*,S*,R*,S*)-17 and a decreasing fraction of it in this sequence of the other diastereomers.