Cooperativity and Feedback Mechanisms in the Single-Crystal-to-Single-Crystal Solid-State Diels–Alder Reaction of 9‑Methylanthracene with Bis(<i>N</i>‑cyclobutylimino)-1,4-dithiin

Electron donor-to-acceptor interactions between 9-methylanthracene and bis­(<i>N</i>-cyclobutylimino)-1,4-dithiin lead to the formation of chiral charge-transfer (CT) crystals. The structure consists of charge-transfer stacks where these two molecules arrange in a 1:1 alternating arrangement. These undergo a topochemical thermal single-crystal-to-single-crystal (SCSC) [2 + 4] Diels–Alder reaction in the solid state. CT crystals were reacted at 40 °C, their structures were determined by X-ray diffraction at various degrees of conversion, and they were examined using Hirshfeld surfaces and lattice energy calculations to find evidence of reaction cooperativity and feedback mechanisms. The results show that steric effects between product molecules and reactant molecules during the SCSC reaction influence the formation of products along the <i>b</i> axis, resulting in a more ordered structure than initially suggested by the crystal structure analysis. A maximum reaction conversion of around 96% was obtained, which indicates that the reaction is also nonrandom within the charge-transfer stacks. Lattice and intramolecular energy calculations show that the energy of an inherently metastable crystal obtained via the SCSC reaction is slightly higher compared to that of the recrystallized product crystal. Finally, structural analysis using CrystalExplorer shows that the shape, size, and surface curvature of the Hirshfeld surface are not much changed by the reaction, indicating that the reaction cavity remains relatively constant and that the reaction is under topochemical control

Do 12-Membered Cycloalkane Rings Only Exist As One Conformation in the Solid-State? A Detailed Solid-State Analysis Involving Polymorphs of <i>N,N</i>′‑Biscyclododecyl Pyromellitic Diimide

Conformational flexibility in molecules plays a key role in many chemical and biological processes. It is a common belief that the larger the cycloalkane the more flexible it will be, and the more conformations it will adopt. While theoretical studies have shown that cyclododecane has many possible conformations, they have also consistently shown that one conformation is slightly more stable. In this work, we examine the effect of substitution and crystal packing on the conformation of singly substituted cyclododecane rings. This has been done by exploiting polymorphism in an attempt to induce new conformations in a specific molecule, as well as by examining structures reported in the Cambridge Structural Database (CSD). To this end, three polymorphs of <i>N,N</i>′-biscyclododecyl pyromellitic diimide (PMDI-12) have been identified and their structures elucidated. To rationalize the differences between the various polymorphs, molecule···molecule interaction energies have been calculated using atom–atom potential methods. Though the conformation of the PMDI-12 molecules as a whole may differ, examination of the conformation of the 12-membered ring indicates that it is conformationally identical in all three polymorphs. Examination of 20 other organic and organometallic structures containing this group in the CSD, indicates that they have the same conformation (only one possible exception in the 34 rings examined in this work), which suggests that the 12-membered ring adopts a single conformation ([3333] with <i>D</i>₂ symmetry) in the solid-state that is relatively unaffected by crystal packing

Do 12-Membered Cycloalkane Rings Only Exist As One Conformation in the Solid-State? A Detailed Solid-State Analysis Involving Polymorphs of <i>N,N</i>′‑Biscyclododecyl Pyromellitic Diimide

Conformational flexibility in molecules plays a key role in many chemical and biological processes. It is a common belief that the larger the cycloalkane the more flexible it will be, and the more conformations it will adopt. While theoretical studies have shown that cyclododecane has many possible conformations, they have also consistently shown that one conformation is slightly more stable. In this work, we examine the effect of substitution and crystal packing on the conformation of singly substituted cyclododecane rings. This has been done by exploiting polymorphism in an attempt to induce new conformations in a specific molecule, as well as by examining structures reported in the Cambridge Structural Database (CSD). To this end, three polymorphs of <i>N,N</i>′-biscyclododecyl pyromellitic diimide (PMDI-12) have been identified and their structures elucidated. To rationalize the differences between the various polymorphs, molecule···molecule interaction energies have been calculated using atom–atom potential methods. Though the conformation of the PMDI-12 molecules as a whole may differ, examination of the conformation of the 12-membered ring indicates that it is conformationally identical in all three polymorphs. Examination of 20 other organic and organometallic structures containing this group in the CSD, indicates that they have the same conformation (only one possible exception in the 34 rings examined in this work), which suggests that the 12-membered ring adopts a single conformation ([3333] with <i>D</i>₂ symmetry) in the solid-state that is relatively unaffected by crystal packing

Do 12-Membered Cycloalkane Rings Only Exist As One Conformation in the Solid-State? A Detailed Solid-State Analysis Involving Polymorphs of <i>N,N</i>′‑Biscyclododecyl Pyromellitic Diimide

Conformational flexibility in molecules plays a key role in many chemical and biological processes. It is a common belief that the larger the cycloalkane the more flexible it will be, and the more conformations it will adopt. While theoretical studies have shown that cyclododecane has many possible conformations, they have also consistently shown that one conformation is slightly more stable. In this work, we examine the effect of substitution and crystal packing on the conformation of singly substituted cyclododecane rings. This has been done by exploiting polymorphism in an attempt to induce new conformations in a specific molecule, as well as by examining structures reported in the Cambridge Structural Database (CSD). To this end, three polymorphs of <i>N,N</i>′-biscyclododecyl pyromellitic diimide (PMDI-12) have been identified and their structures elucidated. To rationalize the differences between the various polymorphs, molecule···molecule interaction energies have been calculated using atom–atom potential methods. Though the conformation of the PMDI-12 molecules as a whole may differ, examination of the conformation of the 12-membered ring indicates that it is conformationally identical in all three polymorphs. Examination of 20 other organic and organometallic structures containing this group in the CSD, indicates that they have the same conformation (only one possible exception in the 34 rings examined in this work), which suggests that the 12-membered ring adopts a single conformation ([3333] with <i>D</i>₂ symmetry) in the solid-state that is relatively unaffected by crystal packing

Iron-57 NMR and Structural Study of [Fe(η⁵‑Cp)(SnPh₃)(CO)(PR₃)] (PR₃ = Phosphine, Phosphite). Separation of Steric and Electronic σ and π Effects

The complexes [Fe­(Cp)­(SnPh₃)­(CO)­(PR₃)] (PR₃ = PMe₃ (<b>1</b>), PⁿBu₃ (<b>2</b>), PCy₃ (<b>3</b>), PMe₂Ph (<b>4</b>), PMePh₂ (<b>5</b>), P­(CH₂Ph)₃ (<b>6</b>), PPh₃ (<b>7</b>), P­(4-MeC₆H₄)₃ (<b>8</b>), P­(4-MeOC₆H₄)₃ (<b>9</b>), P­(4-FC₆H₄)₃ (<b>10</b>), P­(4-CF₃C₆H₄)₃ (<b>11</b>), P­(NMe₂)₃ (<b>12</b>), P­(OMe)₃ (<b>13</b>), P­(OPh)₃ (<b>14</b>)), which have been characterized by X-ray crystallography (except for <b>1</b> and <b>4</b>), infrared spectroscopy (carbonyl stretching frequency, ν_CO), and NMR spectroscopy (¹³C, ³¹P, ⁵⁷Fe, ¹¹⁹Sn) offer some insight into the response of the iron nucleus to changes in the electronic and steric properties of the PR₃ ligand. A fairly good correlation is found between the ⁵⁷Fe chemical shift and the Tolman cone angle θ for PR₃ and a rather poorer correlation between δ­(⁵⁷Fe) and ν_CO. However, for the subseries of complexes <b>7</b>–<b>11</b> having PR₃ = P­(4-XC₆H₄)₃ (X = H, Me, MeO, F, CF₃), the correlation between δ­(⁵⁷Fe) and ν_CO is very good. Since the steric properties of these ligands, from the point of view of the metal, are identical (θ = 145°), this provides a means of separating the steric and electronic contributions of PR₃ to δ­(⁵⁷Fe). The electronic contribution of PR₃ to δ­(⁵⁷Fe) can be further separated into σ and π components by making use of the finding that the π component of the Fe–P bond has a negligible influence on δ­(⁵⁷Fe), unlike its influence on ν_CO. The ligands PMe_3, PⁿBu₃, PCy₃, PMe₂Ph, PMePh₂, and P­(NMe₂)₃ are found to be “pure” σ donors, P­(OMe)₃ and P­(OPh)₃ are found to be π acceptors of differing strength, and P­(4-XC₆H₄)₃ is found to show weak but clearly distinguishable π acceptor properties

Pengembangan Protokol Media Untuk Kultur Embrio Kelapa Kopyor (Coco Nucifera L.) Di Jawa Tlmur

Dalam USAha untuk mendapatkan kelapa Kopyor yang true-to-type, satu-satunya cara adalah dengan menginokulasikan embrio dalam media buatan pada kondisi in-vitro. Ada lima (5) protokol media dengan media dasar Y3 (Eeuwens) dan MS (Murashige &amp; Skoog) yang dicoba yaitu M1 (Protokol UPLB/Philippines) sebagai kontrol, M2 (Protokol I) dengan rangkaian Y3 cair; Y3 cair; Y3 cair (media Y3 cair pada tahap inisiasi ; Y3 cair sub kultur I dan Y3 cair sub kultur II), M3 (Protokol II) dengan rangkaian media Y3 padat; Y3 padat; Y3 padat, ~ (Protokol III) dengan rangkaian media MS padat; MS padat; MS padat, ~ (Protokol IV) dengan rangkaian media Y3 cair; MS padat; Y3 cair, ~ (Protokol V) dengan rangkaian media MS cair; Y3 padat ;Y3 cair. Pertumbuhan embrio kelapa Kopyor sangat capat pada Protokol media II (serangkaian Y3 padat pad a tahap inisiasi, subkultur I dan II), sehingga menjadi plantlet yang sempurna. Sebaliknya pada protokol media I (serangkaian Y3 cair) embrio hanya membesar tetapi tidak dapat berkecambah. Pad a Protokol III embrio memberikan respon yang positif meskipun perkembangan embrio tidak secepat seperti pada protokol II. Pertumbuhan embrio terhenti atau mengalami stagnasi pada serangkain media protokol IV

Polymorphic Diversity: <i>N</i>‑Phenylbenzamide as a Possible Polymorphophore

In this work, we identify and describe a moiety that may be capable of encouraging the formation of polymorphs. Four new <i>N</i>-phenylbenzamide-based compounds have been synthesized yielding four pairs of polymorphs upon recrystallization. The structures of these have been discussed and compared with the previously reported polymorphs of <i>N</i>-[2-(hydroxymethyl)­phenyl]­benzamide. The results indicate that the conformation of the <i>N</i>-phenylbenzamide group is generally constant but is sometimes altered by the crystal packing. The <i>N</i>-phenylbenzamide group is capable of intermolecular N–H···O hydrogen bonding but requires a change in conformation which is generally resisted by the molecule. As a consequence, weak forces such as C–H···O, C–H···N, C–H···π, and π···π interactions play significant but varying roles in these structures. One possible reason for the varying nature of the π···π interactions may be due to the variation of the electrostatic potential across the <i>N</i>-phenylbenzamide group in which negative and positive regions alternate across the face of the molecule. It is the combination of all these attributes that possibly leads to polymorphism being observed in the structures reported here

The Synthesis of a Corrole Analogue of Aquacobalamin (Vitamin B_12a) and Its Ligand Substitution Reactions

The synthesis of a Co­(III) corrole, [10-(2-[[4-(1<i>H</i>-imidazol-1-ylmethyl)­benzoyl]­amino]­phenyl)-5,15-diphenylcorrolato]­cobalt­(III), DPTC-Co, bearing a tail motif terminating in an imidazole ligand that coordinates Co­(III), is described. The corrole therefore places Co­(III) in a similar environment to that in aquacobalamin (vitamin B_12a, H₂OCbl⁺) but with a different equatorial ligand. In coordinating solvents, DPTC-Co is a mixture of five- and six-coordinate species, with a solvent molecule occupying the axial coordination site trans to the proximal imidazole ligand. In an 80:20 MeOH/H₂O solution, allowed to age for about 1 h, the predominant species is the six-coordinate aqua species [H₂O–DPTC-Co]. It is monomeric at least up to concentrations of 60 μM. The coordinated H₂O has a p<i>K</i>_a = 9.76(6). Under the same conditions H₂OCbl⁺ has a p<i>K</i>_a = 7.40(2). Equilibrium constants for the substitution of coordinated H₂O by exogenous ligands are reported as log <i>K</i> values for neutral N-, P-, and S-donor ligands, and CN^–, NO₂^–, N₃^–, SCN^–, I^–, and Cys in 80:20 MeOH/H₂O solution at low ionic strength. The log <i>K</i> values for [H₂O–DPTC-Co] correlate reasonably well with those for H₂OCbl⁺; therefore, Co­(III) displays a similar behavior toward these ligands irrespective of whether the equatorial ligand is a corrole or a corrin. Pyridine is an exception; it is poorly coordinated by H₂OCbl⁺ because of the sterically hindered coordination site of the corrin. With few exceptions, [H₂O–DPTC-Co] has a higher affinity for neutral ligands than H₂OCbl⁺, but the converse is true for anionic ligands. Density functional theory (DFT) models (BP86/TZVP) show that the Co–ligand bonds tend to be longer in corrin than in corrole complexes, explaining the higher affinity of the latter for neutral ligands. It is argued that the residual charge at the metal center (+2 in corrin, 0 in corrole) increases the affinity of H₂OCbl⁺ for anionic ligands through an electrostatic attraction. The topological properties of the electron density in the DFT-modeled compounds are used to explore the nature of the bonding between the metal and the ligands