Utilization of three-dimensional framework theory in identifying the motivational factors for selecting a postgraduate dental specialty-A pilot study

OBJECTIVES

Three-dimensional framework theory classifies factors influencing career selection into intrinsic, extrinsic, and interpersonal dimensions. The objectives of this pilot research were to assess the psychometric properties of a scale encompassing factors affecting post-graduation specialty selection according to three-dimensional framework theory and identify motivational factors that affect dental students' and interns' choice of post-graduation specialty.

METHODOLOGY

A closed-ended self-structured research instrument consisting of a list of 19 factors was presented to dental students and dental interns at Margalla Dental College, Rawalpindi, Pakistan, and Islamic International Dental College, Islamabad, Pakistan (n = 235). Exploratory factor analysis and Cronbach-alpha (α) were used to assess the construct validity and reliability (internal consistency) of the scale respectively. Descriptive analysis and non-parametric tests were used for data analysis with a level of significance at ≤0.05.

RESULTS

A 3-factor solution with 11 items was stabilized. Cronbach-alpha of the pilot study turned out to be 0.72. With a response rate of 92.15%, the most common motivational factor affecting post-graduation specialty selection was the Intrinsic factor "personnel joy and motivation to work hard." Dental interns and male participants were more likely to select the post-graduation specialty due to intrinsic motivational factors (p < 0.05). Inspiration from the family member and supporting the family also influenced male participants and interns respectively (p < 0.05). Female participants preferred to choose a less saturated field (p < 0.05). A medium positive statistically significant correlation was observed between the interpersonal motivational factor "inspiration by a teacher" and the choice of "basic sciences" as a post-graduation specialty (p < 0.01).

CONCLUSION

This pilot study resulted in the development of a scale with a 3-factor solution stabilized at 11 items. The internal consistency of the scale turned out to be 0.72. Oral and maxillofacial surgery was the first choice of post-graduation chosen by 35.5% of the respondents. Fellowship was chosen as the preferred type of post-graduation by 46% of the respondents. Irrespective of gender and designation, the top most influential factor, chosen by 88.5% of the respondents, was the intrinsic motivational factor "personal joy and motivation to work hard."

Pillar[5]arene-Integrated Three-Dimensional Framework Polymers for Macrocycle-Induced Size-Selective Catalysis

Size-selective catalysis is of key importance in the conversion of crude oil or biomass. Here, we fabricate three pillar[5]arene-integrated porous organic polymers with three-dimensional (3D) network structures using 3D cross-linkers. The resulting polymers possess a high surface-to-mass ratio and exhibit exceptional size-selective catalysis in Knoevenagel condensation reactions. In addition, a mechanistic study indicates that the size-selective catalysis is due to the host-guest interaction between pillar[5]arene and substrates. This study suggests that macrocycle-containing polymers could be a promising candidate for size-selective catalysis.

A cadmium(II) coordination polymer with a fivefold interpenetrating diamondoid three-dimensional framework: synthesis, crystal structure, luminescence and photocatalytic properties

A novel three-dimensional (3D) Cd^II coordination polymer, namely, poly[[μ₂-4,4'-bis(2-methylimidazol-1-yl)-[1,1'-biphenyl]](μ₂-5-methylisophthalato)cadmium(II)], [Cd(C₉H₆O₄)(C₂₀H₁₈N₄)]_n or [Cd(MIP)(4,4'-BMIBP)]_n, (I), was synthesized by the hydrothermal method using 5-methylisophthalic acid (H₂MIP), 4,4'-bis(2-methylimidazol-1-yl)-[1,1'-biphenyl] (4,4'-BMIBP) and Cd(NO₃)₂·6H₂O, and characterized by single-crystal X-ray diffraction, elemental analysis, IR spectroscopy and thermogravimetric analysis. Compound (I) exhibits a novel fivefold interpenetrating 3D diamondoid framework. Additionally, it shows fluorescence emission in the solid state and promising photocatalytic activities for the degradation of methylene blue (MB) in water at room temperature.

An Electrically Conducting Three-Dimensional Iron-Catecholate Porous Framework

We report the synthesis of a unique cubic metal–organic framework (MOF), Fe‐HHTP‐MOF, comprising hexahydroxytriphenylene (HHTP) supertetrahedral units and Fe^III ions, arranged in a diamond topology. The MOF is synthesized under solvothermal conditions, yielding a highly crystalline, deep black powder, with crystallites of 300–500 nm size and tetrahedral morphology. Nitrogen sorption analysis indicates a highly porous material with a surface area exceeding 1400 m² g⁻¹. Furthermore, Fe‐HHTP‐MOF shows broadband absorption from 475 up to 1900 nm with excellent absorption capability of 98.5 % of the incoming light over the visible spectral region. Electrical conductivity measurements of pressed pellets reveal a high intrinsic electrical conductivity of up to 10⁻³ S cm⁻¹. Quantum mechanical calculations predict Fe‐HHTP‐MOF to be an efficient electron conductor, exhibiting continuous charge‐carrier pathways throughout the structure.

Crystal structure of poly[di-aqua-bis-(μ5-benzene-1,3-di-carboxyl-ato)(N,N-di-methyl-formamide)-cadmium(II)disodium(I)]

A novel three-dimensional bimetallic Cd^II–Na^I metal–organic framework has been synthesized and the X-ray structure has been reported.

The title compound, [CdNa₂(C₈H₄O₄)₂(C₃H₇NO)(H₂O)₂]_n or [CdNa₂(1,3-bdc)₂(DMF)(H₂O)₂]_n, is a new Cd^II–Na^I heterobimetallic coordination polymer. The asymmetric unit consists of one Cd^II atom, two Na^I atoms, two 1,3-bdc ligands, two coordinated water mol­ecules and one coordinated DMF mol­ecule. The Cd^II atom exhibits a seven-coordinate geometry, while the Na^I atoms can be considered to be penta­coordinate. The metal ions and their symmetry-related equivalents are connected via chelating–bridging carboxyl­ate groups of the 1,3-bdc ligands to generate a three-dimensional framework. In the crystal, there are classical O—H⋯O hydrogen bonds involving the coordinated water mol­ecules and the 1,3-bdc carboxyl­ate groups and π–π stacking between the benzene rings of the 1,3-bdc ligands present within the frameworks.

Synthesis and characterization of two novel bimetallic macrocyclic complexes generated from 1,2,4-triazole-containing semi-rigid ligands and M(NO3)2 units (M = Ni and Zn)

Bimetallic macrocyclic complexes have attracted the attention of chemists and various organic ligands have been used as molecular building blocks, but supramolecular complexes based on semi-rigid organic ligands containing 1,2,4-triazole have remained rare until recently. It is easier to obtain novel topologies by making use of asymmetric semi-rigid ligands in the self-assembly process than by making use of rigid ligands. A new semi-rigid ligand, 3-[(pyridin-4-ylmethyl)sulfanyl]-5-(quinolin-2-yl)-4H-1,2,4-triazol-4-amine (L), has been synthesized and used to generate two novel bimetallic macrocycle complexes, namely bis{μ-3-[(pyridin-4-ylmethyl)sulfanyl]-5-(quinolin-2-yl)-4H-1,2,4-triazol-4-amine}bis[(methanol-κO)(nitrato-κ(2)O,O')nickel(II)] dinitrate, [Ni2(NO3)2(C17H14N6S)2(CH3OH)2](NO3)2, (I), and bis{μ-3-[(pyridin-4-ylmethyl)sulfanyl]-5-(quinolin-2-yl)-4H-1,2,4-triazol-4-amine}bis[(methanol-κO)(nitrato-κ(2)O,O')zinc(II)] dinitrate, [Zn2(NO3)2(C17H14N6S)2(CH3OH)2](NO3)2, (II), by solution reactions with the inorganic salts M(NO3)2 (M = Ni and Zn, respectively) in mixed solvents. In (I), two Ni(II) cations with the same coordination environment are linked by L ligands through Ni-N bonds to form a bimetallic ring. Compound (I) is extended into a two-dimensional network in the crystallographic ac plane via N-H...O, O-H...N and O-H...O hydrogen bonds, and neighbouring two-dimensional planes are parallel and form a three-dimensional structure via π-π stacking. Compound (II) contains two bimetallic rings with the same coordination environment of the Zn(II) cations. The Zn(II) cations are bridged by L ligands through Zn-N bonds to form the bimetallic rings. One type of bimetallic ring constructs a one-dimensional nanotube via O-H...O and N-H...O hydrogen bonds along the crystallographic a direction, and the other constructs zero-dimensional molecular cages via O-H...O and N-H...O hydrogen bonds. They are interlinked into a two-dimensional network in the ac plane through extensive N-H...O hydrogen bonds, and a three-dimensional supramolecular architecture is formed via π-π interactions between the centroids of the benzene rings of the quinoline ring systems.

Crystal structure of piperazine-1,4-diium bis-(4-amino-benzene-sulfonate)

The asymmetric unit of the title salt, C4H12N2 (2+)·2C6H6NO3S(-), consists of half a piperazindiium dication, located about an inversion centre, and a 4-amino-benzene-sulfonate anion. The piperazine ring adopts a chair conformation. In the crystal, the cations and anions are linked via N-H⋯O and C-H⋯O hydrogen bonds, forming a three-dimensional framework. Within the framework there are C-H⋯π inter-actions and the N-H⋯O hydrogen bonds result in the formation of R 4 (4)(22) and R 3 (4)(13) ring motifs.

Crystal structure of (S)-2-amino-2-methyl-succinic acid

The title compound, C₅H₉NO₄, crystallized as a zwitterion. There is an intra­molecular N—H⋯O hydrogen bond involving the trans-succinic acid and the ammonium group, forming an S(6) ring motif. In the crystal, mol­ecules are linked by O—H⋯O hydrogen bonds, forming C(7) chains along the c-axis direction. The chains are linked by N—H⋯O and C—H⋯O hydrogen bonds, forming sheets parallel to the bc plane. Further N—H⋯O hydrogen bonds link the sheets to form a three-dimensional framework.

Crystal structures of {[Cu(Lpn)2][Fe(CN)5(NO)]·H2O} n and {[Cu(Lpn)2]3[Cr(CN)6]2·5H2O} n [where Lpn = (R)-propane-1,2-di-amine]: two heterometallic chiral cyanide-bridged coordination polymers

The title compounds, catena-poly[[[bis-[(R)-propane-1,2-di-amine-κ(2) N,N']copper(II)]-μ-cyanido-κ(2) N:C-[tris-(cyanido-κC)(nitroso-κN)iron(III)]-μ-cyanido-κ(2) C:N] monohydrate], {[Cu(Lpn)2][Fe(CN)5(NO)]·H2O} n , (I), and poly[[hexa-μ-cyanido-κ(12) C:N-hexa-cyanido-κ(6) C-hexa-kis-[(R)-propane-1,2-di-amine-κ(2) N,N']dichromium(III)tricopper(II)] penta-hydrate], {[Cu(Lpn)2]3[Cr(CN)6]2·5H2O} n , (II) [where Lpn = (R)-propane-1,2-di-amine, C3H10N2], are new chiral cyanide-bridged bimetallic coordination polymers. The asymmetric unit of compound (I) is composed of two independent cation-anion units of {[Cu(Lpn)2][Fe(CN)5)(NO)]} and two water mol-ecules. The Fe(III) atoms have distorted octa-hedral geometries, while the Cu(II) atoms can be considered to be penta-coordinate. In the crystal, however, the units align to form zigzag cyanide-bridged chains propagating along [101]. Hence, the Cu(II) atoms have distorted octa-hedral coordination spheres with extremely long semicoordination Cu-N(cyanido) bridging bonds. The chains are linked by O-H⋯N and N-H⋯N hydrogen bonds, forming two-dimensional networks parallel to (010), and the networks are linked via N-H⋯O and N-H⋯N hydrogen bonds, forming a three-dimensional framework. Compound (II) is a two-dimensional cyanide-bridged coordination polymer. The asymmetric unit is composed of two chiral {[Cu(Lpn)2][Cr(CN)6]}(-) anions bridged by a chiral [Cu(Lpn)2](2+) cation and five water mol-ecules of crystallization. Both the Cr(III) atoms and the central Cu(II) atom have distorted octa-hedral geometries. The coordination spheres of the outer Cu(II) atoms of the asymmetric unit can be considered to be penta-coordinate. In the crystal, these units are bridged by long semicoordination Cu-N(cyanide) bridging bonds forming a two-dimensional network, hence these Cu(II) atoms now have distorted octa-hedral geometries. The networks, which lie parallel to (10-1), are linked via O-H⋯O, O-H⋯N, N-H⋯O and N-H⋯N hydrogen bonds involving all five non-coordinating water mol-ecules, the cyanide N atoms and the NH2 groups of the Lpn ligands, forming a three-dimensional framework.

Three-dimensional hierarchical frameworks based on MoS₂ nanosheets self-assembled on graphene oxide for efficient electrocatalytic hydrogen evolution

Advanced materials for electrocatalytic water splitting are central to renewable energy research. In this work, three-dimensional (3D) hierarchical frameworks based on the self-assembly of MoS2 nanosheets on graphene oxide were produced via a simple one-step hydrothermal process. The structures of the resulting 3D frameworks were characterized by using a variety of microscopic and spectroscopic tools, including scanning and transmission electron microscopies, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman scattering. Importantly, the three-dimensional MoS2/graphene frameworks might be used directly as working electrodes which exhibited apparent and stable electrocatalytic activity in hydrogen evolution reaction (HER), as manifested by a large cathodic current density with a small overpotential of -107 mV (-121 mV when loaded on a glassy-carbon electrode) and a Tafel slope of 86.3 mV/dec (46.3 mV/dec when loaded on a glassy-carbon electrode). The remarkable performance might be ascribed to the good mechanical strength and high electrical conductivity of the 3D frameworks for fast charge transport and collection, where graphene oxide provided abundant nucleation sites for MoS2 deposition and oxygen incorporation led to the formation of defect-rich MoS2 nanosheets with active sites for HER.

A pillared framework coordination polymer based on the Cd3(μ3-OH) unit: poly[[(μ4-5-aminotetrazolato-κ(4)N(1):N(2):N(3):N(4))chlorido-μ3-hydroxido-(μ3-isonicotinato-κ(3)N:O:O')dicadmium(II)] 0.14-hydrate]

The title coordination polymer, {[Cd2(CH2N5)(C6H4NO2)Cl(OH)]·0.14H2O}n, (I), was synthesized by the reaction of cadmium acetate and N-(1H-tetrazol-5-yl)isonicotinamide in aqueous ammonia, using hydrochloric acid to adjust the pH. Under hydrothermal conditions, N-(1H-tetrazol-5-yl)isonicotinamide slowly hydrolyzes to form isonicotinic acid (Hisonic) and 5-aminotetrazole (Hatz). The deprotonated form of isonicotinic acid (denoted isonic) acts as a bridging ligand in the structure. The polymer crystallizes in the monoclinic space group C2/m. In the structure, there is one Cd3(μ3-OH) unit of Cs symmetry, with one of the Cd(II) atoms and the O and H atoms located on a mirror plane. The other crystallographically independent Cd(II) cation is located on an inversion centre. Each edge of the Cd3(μ3-OH) isosceles triangle is bridged by an atz ligand in a μ1,2 or μ2,3/μ3,4 mode. The Cd3(μ3-OH) units are laced around with a belt of chloride ligands. The belts are further connected into undulating layers via weak inter-belt Cd-Cl bonds. The two organic ligands reside across mirror planes. The construction of a three-dimensional framework is completed by the pillaring isonic ligand. Water molecules partially occupy the voids of the framework.

Synthesis on winged graphene nanofibers and their electrochemical capacitive performance

Assembly techniques of graphene have attracted intense attention since their performance strongly depends on the manners in which graphene nanosheets are arranged. In this work, we demonstrate a viable process to synthesize winged graphene nanofibers (G-NFs) which could generate optimized pore size distribution by the fiber-like feature of graphene. The G-NF frameworks were achieved by processing the precursor graphene oxide nanosheets with the following procedures: microwave (MW) irradiation, salt addition, freeze-drying, and chemical reduction. The resultant framework composed of winged G-NFs with a diameter of 200-500 nm and a length of 5-20 μm. Moreover, the crimp degree of G-NFs can be rationally controlled by MW irradiation time. A formation mechanism of such winged G-NFs based on the synergistic effects from MW irradiation and solution ionic strength change has been proposed. With a practice in flexible electrode, after decorated with amorphous MnO2, the G-NF frameworks shows an enhanced specific capacitance compared to graphene nanosheets (G-NSs). This research has developed a controllable method to synthesis G-NFs, which can offer hierarchical pore structures, this kind of graphene nanostructure might enhance their performance in supercapacitor and related fields.

A three-dimensional Zn(II) coordination framework: poly[[μ2-(E)-1,2-bis(pyridin-4-yl)ethene][μ4-(E)-2,2'-(diazene-1,2-diyl)dibenzoato][μ2-(E)-2,2'-(diazene-1,2-diyl)dibenzoato]dizinc(II)]

In the title coordination polymer, [Zn2(C14H8N2O4)2(C12H10N2)]n, the asymmetric unit contains one Zn(II) cation, two halves of 2,2'-(diazene-1,2-diyl)dibenzoate anions (denoted L(2-)) and half of a 1,2-bis(pyridin-4-yl)ethene ligand (denoted bpe). The three ligands lie across crystallographic inversion centres. Each Zn(II) centre is four-coordinated by three O atoms of bridging carboxylate groups from three L(2-) ligands and by one N atom from a bpe ligand, forming a tetrahedral coordination geometry. Two Zn(II) atoms are bridged by two carboxylate groups of L(2-) ligands, generating a [Zn2(CO2)2] ring. Each loop serves as a fourfold node, which links its four equivalent nodes via the sharing of four L(2-) ligands to form a two-dimensional [Zn2L4]n net. These nets are separated by bpe ligands acting as spacers, producing a three-dimensional framework with a 4(6)6(4) topology. Powder X-ray diffraction and solid-state photoluminescence were also measured.