Interplay between Polymorphism and Isostructurality in the 2-Fur- and 2-Thenaldehyde Semi- and Thiosemicarbazones

The four compounds, namely: 5-nitro-2-furaldehyde thiosemicarbazone (1); 5-nitro-2-thiophene thiosemicarbazone (2); 5-nitro-2-furaldehyde semicarbazone (3); and 5-nitro-2-thiophene semicarbazone (4) were synthesized and crystallized. The three new crystal structures of 1, 2, and 4 were determined and compared to three already known crystal structures of 3. Additionally, two new polymorphic forms of 1 solvate were synthesized and studied. The influence of the exchange of 2-thiophene to 2-furaldehyde as well as thiosemicarbazone and semicarbazone on the self-assembly of supramolecular nets was elucidated and discussed in terms of the formed synthons and assemblies accompanied by Full Interaction Maps analysis. Changes in the strength of IR oscillators caused by the molecular and crystal packing effects are described and explained in terms of changes of electron density.

Tuning the Bonding of a μ-Mesityl Ligand on Dicopper(I) through a Proton-Responsive Expanded PNNP Pincer Ligand

<p>We report the synthesis and characterization of a series of cationic, neutral and anionic dicopper(I) complexes featuring a <i>µ</i>-mesityl ligand and a naphthyridine-derived PNNP expanded pincer ligand. Structural characterization showed that the protonation state of the dinucleating ligand has a pronounced effect on the bending and tilting of the <i>µ</i>-mesityl ligand. DFT calculations indicate that the varying orientations of the <i>µ</i>-mesityl ligand are inherent due to changes in electronic structure rather than crystal packing effects. NBO analysis reveals how the interactions that contribute to the 3-center 2-electron bond between the <i>µ</i>-mesityl ligand and the dicopper core change for the various degrees of observed bending and tilting. </p>

Tuning the Bonding of a μ-Mesityl Ligand on Dicopper(I) through a Proton-Responsive Expanded PNNP Pincer Ligand

<p>We report the synthesis and characterization of a series of cationic, neutral and anionic dicopper(I) complexes featuring a <i>µ</i>-mesityl ligand and a naphthyridine-derived PNNP expanded pincer ligand. Structural characterization showed that the protonation state of the dinucleating ligand has a pronounced effect on the bending and tilting of the <i>µ</i>-mesityl ligand. DFT calculations indicate that the varying orientations of the <i>µ</i>-mesityl ligand are inherent due to changes in electronic structure rather than crystal packing effects. NBO analysis reveals how the interactions that contribute to the 3-center 2-electron bond between the <i>µ</i>-mesityl ligand and the dicopper core change for the various degrees of observed bending and tilting. </p>

Deciphering crystal packing effects in the spin crossover of six [FeII(2-pic)3]Cl2 solvatomorphs

Six isostructural solvatomorphs of the same Fe(ii) complex have been reported to display completely different SCO transitions due to tiny differences in their crystal environments. In this paper, we unravel the reasons.

Evidence of crystal packing effects in stabilizing high or low spin states of iron(ii) complexes with functionalized 2,6-bis(pyrazol-1-yl)pyridine ligands

High or low spin states in iron(ii) complexes with functionalised 2,6-bis(pyrazol-1-yl)pyridine ligands are efficaciously driven by intermolecular contacts.

Crystal Structure Optimization and Semi-Empirical Quantum Chemical Calculations of Fused Bicyclic Heterocycles

The crystal structures of two fused pyridine derivatives viz Ethyl 3-amino-6-phenyl-4-tolylfuro[2,3-b]pyridine-2-carboxylate (I) and Ethyl 3-amino-6-phenyl-4-tolylthieno[2,3-b] pyridine-2-carboxylate (II) were optimized by semi-empirical methods using MOPAC2009 program. The geometries optimized for both the structures from Austin Model 1 (AM1) and Parametrization Model 6 (PM6) describe the conformational discrepancy and crystal packing effects. The parametric molecular electrostatic potential (PMEP) calculated by AM1 semi-empirical method describe the involvement of nitrogen and oxygen atoms in the crystal packing interactions in both the structures. The frontier molecular orbitals highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) indicate the intramolecular charge transfer interactions. The HOMED indices computed for the phenyl rings in the structures describe the p-electron delocalization. The linear regression analysis shows good correlation between experimental and theoretical structures.

Polymorph crystal packing effects on charge transfer emission in the solid state

Condensation of 1,8-naphthalic anhydride with N,N-(dimethylamino)aniline produced the donor-acceptor compound DMIM, which crystallised from a chloroform–diethyl ether mixture to afford two different coloured crystal polymorphs.