A new fluorinated binuclear copper (II) bromide complex, [(CF3CH2OCH2py)2CuBr2]2, incorporating trifluoromethyl substituents, has been synthesized and fully characterized. Single-crystal X-ray diffraction reveals a centrosymmetric dimer in the triclinic space group P-1 where each Cu (II) center adopts a five-coordinate distorted square-pyramidal geometry. In addition, the structure exhibits several intra- and inter-molecular noncovalent interactions, including C–H···X(-M) blue-shifting hydrogen bonding and C···F tetrel bonding. An intramolecular C1···F1 TB is observed; and this TB has the significant effects on the distances of two methylene C–H bonds, leading to a local mode behavior. FT-IR analysis clearly supports this C–H bond change effect, showing two distinct methylene C–H vibrational peaks: one red-shifted peak at 2755 cm− 1 and the other blue-shifted peak at 2990 cm− 1. These results confirm that two methylene C–H vibrations are decoupled such that each of two methylene C–H bonds independently vibrates like a methine bond. Interestingly, the F-containing moiety engaging in intermolecular C–F···C TB with the pyridyl ring can collaborate with intermolecular blue-shifting C–H···Br(–M) HB in directing molecular orientation, so these non-covalent interactions then assist in forming the antiparallel displaced π–π stacking between two pyridyl rings to help the supramolecular assembly. Furthermore, the magnetic properties of this fluorinated Cu complex have been studied.
Two Schiff bases, 4-bromo-2-[(cyclopentylimino)methyl]phenol (HL1) and 4-bromo-2-[(cyclohexylimino)methyl]phenol (HL2), were used to prepare two cobalt complexes, [Co(L1)3] (1) and [Co(L2)2] (2). The compounds were characterized by IR and UV–Vis spectroscopy and single crystal X-ray diffraction. Complex 1 contains a six-coordinate, distorted octahedral Co(III) center with three bidentate O, N-donor ligands, whereas complex 2 contains a four-coordinate, distorted tetrahedral Co(II) center with two bidentate ligands. The distinct structures are consistent with an influence of the N-alkyl substituent on coordination and product formation; however, the present comparison of two isolated products does not establish steric bulk as the sole cause of the different oxidation states. In the jack bean urease assay, complex 1 showed 73 ± 3
Herbicides play a very important role in modern agriculture by suppressing weed production and ensuring agricultural yield. However, the uncontrolled release of herbicides is an environmental problem that leads to long-term soil and water contamination. To ensure a cleaner ecosystem, it is important to develop effective materials that can selectively encapsulate residues of herbicides. Carbon nanobelt (CNB) has been explored in this work as a novel nanomaterial for encapsulating herbicides and preserving the environment. CNB possesses curved π-conjugated surface which makes it an ideal material for the encapsulation of herbicides through van der Waals forces and π -π stacking. Density functional theory (DFT) has been used to analyze the encapsulation performance of CNB for herbicides, i.e., glyphosate, atrazine, 2,4-dichlorophenoxyaceticacid, and triallate. Several computational descriptors and analyses, such as interaction energy (Eint) analysis, frontier molecular orbital (FMO) analysis, natural bond orbital (NBO) analysis, electron density difference (EDD) analysis, charge decomposition analysis (CDA), non-covalent interaction (NCI) analysis, quantum theory of atoms in molecules (QTAIM) analysis, and recovery time analysis, were considered for evaluating the performance and selectivity of CNB for herbicides. According to the results, the herbicides (investigated) can form favorable host–guest complexes with CNB where noncovalent interactions play a main role. Overall, the results give a molecular-level understanding of the interaction mechanisms between herbicides and CNB and propose the potential applicability of CNB as a host material for encapsulation of herbicides. The current study may provide a computational basis for further investigation of systems with herbicides encapsulated in CNB; however, experimental studies under realistic environmental conditions are necessary to evaluate their practical applicability.
Positional substitution can modify the electronic and nonlinear optical (NLO) responses of conjugated molecules without changing their donor and acceptor identities. Here, DFT and TD-DFT calculations were performed for 15 benzo[1,2-b:4,5-b′]dithiophene (BDT) derivatives, including four composition-matched donor/acceptor pairs in the 2,6 and 3,7 arrangements. Across all four pairs, the 2,6 derivatives exhibit larger calculated static and 1064 nm first-hyperpolarizability magnitudes than their 3,7 counterparts. The static orientationally averaged second hyperpolarizability follows the same positional ordering. Among the investigated derivatives, 2,6-NH2/NO2 has the largest static first-hyperpolarizability magnitude (1.15 × 104 a.u.), whereas 2,6-SCH3/NO2 has the largest static orientationally averaged second hyperpolarizability (1.2 × 105 a.u.). An integrated analysis of natural transition orbitals, hole-electron distributions, charge-density differences, and fragment transition-density matrices reveals distinct organizations of the selected excited states. For the representative NH2/NO2 pair, the 3,7 derivative exhibits greater spatial charge separation in its selected bright state, despite having a smaller calculated first-hyperpolarizability magnitude. Thus, the positional NLO trend cannot be explained by charge-transfer distance or the HOMO-LUMO separation alone. Selected functional-sensitivity and orientationally averaged hyper-Rayleigh-scattering calculations provide complementary molecular comparisons, while fixed-geometry continuum-solvent calculations examine the dielectric-environment dependence of selected responses. These results establish a positional dependence of the calculated molecular NLO response for the composition-matched BDT derivatives.
How a dopant changes the second-order optical response of a cluster depends on the structure it creates as much as on its electronic character. We examine this for six hydrogenated boron–germanium model clusters arranged as three matched pairs, in which two boron-bound H atoms of an undoped framework (GB1–GB3) are replaced by Cu (GB4–GB6). All six structures were fully optimized, and all properties were evaluated consistently at the CAM-B3LYP/6–31 + G(d, p) level (point groups: GB1, GB4, GB5 C2v, GB3, GB6 C2h, GB2 C1). Cu capping narrows the Koopmans gap (6.95→5.81, 5.95→5.42 and 5.61→5.06 eV) and lowers the electrophilicity. It also increases the isotropic polarizability in every pair (⟨α⟩ = 93–127 a.u. undoped versus 165–205 a.u. Cu-capped). By contrast, the static first hyperpolarizability follows point-group symmetry. The β0 rises from 45.5 to 1116.1 a.u. (GB1 → GB4, C2v) and changes only from 117.3 to 122.5 a.u. (GB2 → GB5), but it remains zero in the centrosymmetric pair GB3 → GB6 (C2h) despite a 1.3-fold increase in ⟨α⟩. GB4 reaches 38 times the β0 of urea computed at the same level. TD-DFT hole–electron and transition-density (Ω) analyses show that Cu supplies both a Cu-rich occupied level and a Cu-centered acceptor level (57
