Flexible Porous Coordination Polymers from Divergent Photoluminescent 4‑Oxo-1,8-naphthalimide Ligands

Two new luminescent ditopic naphthalimide-derived ligands, <i>N</i>-(4-cyanophenylmethylene)-4-(4-cyanophenoxy)-1,8-naphthalimide (<b>L3</b>) and <i>N</i>-(4-carboxyphenylmethylene)-4-(4-carboxyphenoxy)-1,8-naphthalimide (<b>H</b>_<b>2</b><b>L4</b>), have been prepared, and their coordination chemistry has been explored in the synthesis of three new coordination polymer materials. Complex poly-[Ag­(<b>L3</b>)₂]­BF₄·4.5H₂O·0.5THF (<b>1</b>) is a 3-fold 2D → 2D parallel interpenetrated coordination polymer in which three interwoven sheets define inter- and intralayer channels containing anions and solvent molecules. Molecules of <b>L3</b> interact in <b>1</b> through dominant head-to-head π–π stacking interactions, in an opposite aggregation mode to that observed in the free ligand in the crystalline phase. Complexes poly-[Cu­(<b>L4</b>)­(OH₂)]·2DMF·0.5H₂O (<b>2</b>) and poly-[Cd₂(<b>L4</b>)₂(OH₂)₂]·1.5DMF·3H₂O (<b>3</b>) are related noninterpenetrated two-dimensional coordination polymers defined by one-dimensional metal–carboxylate chains, forming layers that interdigitate with adjacent networks through naphthalimide π–π interactions. Both materials undergo structural rearrangements on solvent exchange with acetonitrile; in the case of <b>3</b>, this transformation can be followed by single-crystal X-ray diffraction, revealing the structure of the acetonitrile solvate poly-[Cd₂(OH₂)₂(<b>L4</b>)₂]·2MeCN (<b>4</b>), which shows a significant compression of the primary channels to accommodate the solvent guest molecules. Both materials display modest CO₂ adsorption after complete evacuation, and the original expanded phases can be regenerated by reimmersion in DMF. The photophysical properties of each ligand and complex were also explored, which revealed variations in emission wavelength, based on solid-state interactions, including a notable shift in the fluorescence emission band of <b>3</b> upon structural rearrangement to <b>4</b>

Flexible Porous Coordination Polymers from Divergent Photoluminescent 4‑Oxo-1,8-naphthalimide Ligands

Two new luminescent ditopic naphthalimide-derived ligands, <i>N</i>-(4-cyanophenylmethylene)-4-(4-cyanophenoxy)-1,8-naphthalimide (<b>L3</b>) and <i>N</i>-(4-carboxyphenylmethylene)-4-(4-carboxyphenoxy)-1,8-naphthalimide (<b>H</b>_<b>2</b><b>L4</b>), have been prepared, and their coordination chemistry has been explored in the synthesis of three new coordination polymer materials. Complex poly-[Ag­(<b>L3</b>)₂]­BF₄·4.5H₂O·0.5THF (<b>1</b>) is a 3-fold 2D → 2D parallel interpenetrated coordination polymer in which three interwoven sheets define inter- and intralayer channels containing anions and solvent molecules. Molecules of <b>L3</b> interact in <b>1</b> through dominant head-to-head π–π stacking interactions, in an opposite aggregation mode to that observed in the free ligand in the crystalline phase. Complexes poly-[Cu­(<b>L4</b>)­(OH₂)]·2DMF·0.5H₂O (<b>2</b>) and poly-[Cd₂(<b>L4</b>)₂(OH₂)₂]·1.5DMF·3H₂O (<b>3</b>) are related noninterpenetrated two-dimensional coordination polymers defined by one-dimensional metal–carboxylate chains, forming layers that interdigitate with adjacent networks through naphthalimide π–π interactions. Both materials undergo structural rearrangements on solvent exchange with acetonitrile; in the case of <b>3</b>, this transformation can be followed by single-crystal X-ray diffraction, revealing the structure of the acetonitrile solvate poly-[Cd₂(OH₂)₂(<b>L4</b>)₂]·2MeCN (<b>4</b>), which shows a significant compression of the primary channels to accommodate the solvent guest molecules. Both materials display modest CO₂ adsorption after complete evacuation, and the original expanded phases can be regenerated by reimmersion in DMF. The photophysical properties of each ligand and complex were also explored, which revealed variations in emission wavelength, based on solid-state interactions, including a notable shift in the fluorescence emission band of <b>3</b> upon structural rearrangement to <b>4</b>

Influence of Backbone Conformational Rigidity in Temperature-Sensitive Amphiphilic Supramolecular Assemblies

Molecular design features that endow amphiphilic supramolecular assemblies with a unique temperature-sensitive transition have been investigated. We find that conformational rigidity in the backbone is an important feature for eliciting this feature. We also find that intramolecular hydrogen-bonding can induce such rigidity in amphiphile backbone. Guest encapsulation stability of these assemblies was found to be significantly altered within a narrow temperature window, which correlates with the temperature-sensitive size transition of the molecular assembly. Molecular design principles demonstrated here could have broad implications in developing future temperature-responsive systems

A Schiff-base cross-linked supramolecular polymer containing diiminophenol compartments and its interaction with copper(II) ions

<p>We report here the preparation of a Schiff-base linked organic polymer <b>1</b> based on linkages containing the potent supramolecular aggregator benzene-1,3,5-tricarboxamide, connected through 2,6-diiminophenol metal binding pockets into a cross-linked polymer. The morphological and physical properties of this material are studied using electron microscopy techniques, thermal analysis, NMR, fluorescence spectroscopy and gas adsorption studies. The interaction of the polymer <b>1</b> with Cu^II ions is then investigated by soaking the material with methanolic copper acetate solution, and studying the resulting aggregates using EDX microscopy and FTIR spectroscopy. A small-molecule model compound <b>2</b> is also prepared and crystallographically characterised to act as a spectroscopic comparison, providing strong evidence that <b>1</b> interacts with copper ions through a nucleation/seeding mechanism for the growth of microcrystalline copper acetate deposits, rather than via chemisorption of the copper ions within the diiminophenol binding pockets. Preliminary results suggest a similar mechanism for Co^II adsorption, while Zn^II ions exhibit a separate interaction mode.</p

Initial evaluation of the performance of novel inorganic scintillating detectors for small animal irradiation dosimetry

The purpose of this study was to design and evaluate the performance of four novel inorganic scintillating detectors (ISDs) on the Small Animal Radiation Research Platform (SARRP). Relative scintillator output, measurement repeatability, setup uncertainty, linearity with dose rate, and signal reproducibility over time were investigated. The Gd2O2S:Tb detector had the highest relative signal output, generating up to 219 times more charge than a previously characterized BCF-60based plastic scintillating detector (PSD). The Gd2O2S:Tb detector was then used to measure 220 kVp therapy beam profiles of 10 x 10 and 5 x 5 mm2 fields. Beam profiles using the ZnS-based phosphor were also obtained and compared to investigate the performance of a lower density inorganic scintillator. 10 x 10 and 5 x 5 mm2 therapy beam profile measurements made with the Gd2O2S:Tb and BCF-60 detectors differed, on average, by 1.1% and 1.9%, respectively. The ZnS:Ag measurements differed, on average, by 2.5% and 6% relative to BCF-60 measurements of the 10 x 10 and 5 x 5 mm2 beam profiles, respectively. MicroCT imaging of the detector volumes was also performed, revealing poor packing of the ZnS:Ag crystalline phosphor in the deepest region of the cylindrical cavity. The Gd2O2S:Tb detector, in particular, has proven to be a promising candidate for real-time dosimetry of small fields in small animal irradiators, primarily because of the very large signal intensities observed, along with good repeatability, dose rate linearity, reproducibility and agreement with beam profile measurements made with a previously validated detector