How To Draw A Bond (Ionic Or Covalent)

THE CHEMICAL BOND

Therald Moeller , ... Clyde Metz , in Chemical science: With Inorganic Qualitative Analysis, 1980

9.11 Coordinate covalent bonds

A single covalent bail in which both electrons in the shared pair come from the same atom is called a coordinate covalent bond. To signal a coordinate covalent bond an arrow is sometimes drawn from the atom that donates the electron pair toward the atom with which the pair is shared.

The donor atom provides both electrons to a coordinate covalent bond and the acceptor atom accepts an electron pair for sharing in a coordinate covalent bond. For coordinate covalent bonds, as for any other kind of bond, it is impossible to distinguish among the electrons in one case the bond has formed. For case, a hydrogen ion unites with an ammonia molecule by a coordinate covalent bond to grade the ammonium ion

just all four hydrogens in the ammonium ion are akin.

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Structure and Bonding in Organic Compounds

Robert J. Ouellette , J. David Rawn , in Organic Chemical science, 2022

Covalent Bonds

Covalent bonds are much more mutual in organic chemistry than ionic bonds. A covalent bond consists of the simultaneous attraction of two nuclei for 1 or more pairs of electrons. The electrons located between the two nuclei are bonding electrons. Covalent bonds occur between identical atoms or between unlike atoms whose difference in electronegativity is bereft to let transfer of electrons to form ions.

Permit'southward consider the covalent bond in the hydrogen molecule. A hydrogen molecule forms from two hydrogen atoms, each with one electron in a 1   s orbital. The ii hydrogen atoms are attracted to the same pair of electrons in the covalent bail. The bond is represented either as a pair of "dots" or as a solid line. Each hydrogen cantlet acquires a helium-like electron configuration.

$\text{H}•+\text{H}•\to \text{H}••\text{H}\text{or}\text{H}─\text{H}$

Energy is released when the electrons associated with the ii hydrogen atoms form a covalent bond. The procedure releases heat; therefore, it is exothermic. The heat released when one molecule of a compound forms at 298   1000 is the standard enthalpy alter (ΔH°) for the process. ΔH° for forming a mole of hydrogen from two hydrogen atoms is −   435   kJ mole⁻¹. Since energy is released in the reaction, the hydrogen molecule is more stable than the two hydrogen atoms. The opposite process, pulling the two bonded hydrogen atoms apart, requires 435   kJ mole⁻ⁱ, a quantity called the bond strength of the H─H bail.

The two hydrogen nuclei are separated by a altitude called the bond length. This altitude results from a balance between attractive and repulsive forces. There is an allure between the nuclei and the bonding electrons, just there is also a repulsion between the two nuclei equally well as between the 2 electrons. Effigy i.v is a schematic diagram of these attractive and repulsive forces. It provides a starting betoken for our discussion of bonding.

Figure 1.5. Bonding Forces in a Hydrogen Molecule

When a covalent bond forms between 2 hydrogen atoms, there are two sets of electrostatic repulsions (nuclear–nuclear and electron–electron, ruddy), but iv sets of electrostatic attractions (greenish). The attractive forces are equal in magnitude, but opposite in sign. Each hydrogen nucleus attracts both electrons. The net event is that the energy of the organization decreases when the bond forms. This uncomplicated electrostatic model for bonding does not fairly describe chemic bonds. For that we will need to expand our analysis, and we volition exercise that in the following sections.

A covalent bond also occurs in Cl₂. In the chlorine molecule, the two chlorine atoms are attracted to the same pair of electrons. Each chlorine cantlet has 7 valence electrons in the tertiary free energy level and requires one more than electron to form an electron core with an argon electron configuration. Each chlorine atom contributes one electron to the bonded pair shared by the two atoms. The remaining vi valence electrons of each chlorine atom are non involved in bonding. They are variously chosen nonbonding electrons, solitary pair electrons, or unshared electron pairs.

As we noted earlier, a covalent bond is fatigued as a dash in a Lewis structure. Likewise, in a Lewis structure, nonbonding electron pairs are shown as "dots." The Lewis structures of four uncomplicated organic compounds: methane, aminomethane, methanol, and chloromethane are shown beneath with both bonding and nonbonding electrons.

The hydrogen atom and the halogen atoms form only ane covalent bond to other atoms in stable neutral compounds. However, the carbon, oxygen, and nitrogen atoms tin can bail to more than than i atom. The number of covalent bonds an atom tin form is called the valence of the atom. The valence of a given atom is the aforementioned in nigh stable neutral organic compounds. Table 1.2 lists the valences of some common elements contained in organic compounds.

Table i.2. Valences of Common Elements ¹

Atom	Valence
Hydrogen	i
Fluorine	1
Bromine	1
Chlorine	1
Iodine	i
Oxygen	ii
Sulfur	2
Nitrogen	3
Carbon	4

ane

The valence is the usual number of bonds formed by the atom in neutral compounds.

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Review of Basic Organic Chemical science

Eric Stauffer , ... Reta Newman , in Fire Droppings Analysis, 2008

iii.2.3 Covalent Bonds

Covalent bonds are the most important means of bonding in organic chemical science. The formation of a covalent bail is the result of atoms sharing some electrons. The bond is created by the overlapping of ii atomic orbitals [ 1]. This process is illustrated in Figure iii-iv. In this type of bond, each shared electron will exist counted toward both atoms' valence shells for the purpose of satisfying the octet rule. In a single bond one pair of electrons is shared, with one electron beingness contributed from each of the atoms. Double bonds share two pairs of electrons and triple bonds share three pairs of electrons. Bonds sharing more than i pair of electrons are called multiple covalent bonds.

Effigy 3-4a. Two s orbitals form a σ bond.

Figure 3-4b. An s orbital and a p orbital likewise form a σ bail.

FIGURE 3-4c. Ii p orbitals parallel to their internuclear axis also form a σ bond.

(Source: McMurry J an Fay RC (2003) Chemical science, iv^th edition Prentice Hall, Upper Saddle River, NJ. Reprinted with the permission o Prentice Hall, Upper Saddle River, New Jersey, USA.)

In a unmarried covalent bond, when the electrons are shared betwixt 2 s orbitals, the resulting bond is a sigma (σ) bail equally shown in Figure 3-iv. Sigma bonds are the strongest covalent chemic bonds. Sigma bonds as well occur when an southward and a p orbital share a pair of electrons or when 2 p orbitals that are parallel to the internuclear axis share a pair of electrons (see Figure 3-4). A pi (π) bond is the issue of the sharing of a pair of electrons between two p orbitals that are perpendicular to the internuclear axis (see Figure 3-5). In double and triple bonds, the first bond is a σ bond and the second and 3rd ones are π bonds. Pi bonds are weaker than sigma bonds, however a double bond has the combined strength of the σ and π bonds. Analogously, a triple bond has the combined force of a σ and two π bonds. As an case, each of the hydrogen atoms in water (Water) is bonded to the oxygen via a single bond (σ bond) whereas the oxygen atoms in carbon dioxide (CO_two) are bound to the carbon atom via double bonds, each consisting of a σ bond and a π bond.

Effigy 3-5a. Two p orbitals perpendicular to the internuclear axis course a π bond.

Effigy 3-5b. In double bonds, the outset bail is a σ bond and the 2d bond is a π bail. The diagram clearly explains why a double bond tin can no longer rotate on itself.

Effigy 3-5c. In triple bonds, the first bail is a σ bail and the last two bonds are π bonds.

(Source: McMurry J and Fay RC (2003) Chemical science, four^th edition Prentice Hall, Upper Saddle River, NJ. Reprinted with the permission of Prentice Hall, Upper Saddle River, New Bailiwick of jersey, USA.)

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Surface modification of metal oxide nanoparticles to realize biological applications

Nisha Yadav , ... Sanjay Singh , in Reference Module in Materials Science and Materials Engineering, 2022

Covalent Binding

A covalent bond can be represented as a linkage between electron pair and two atoms. Unlike molecules such every bit hydrogen, nitrogen, chlorine, water, ammonia accept a covalent bond, and other ligands with sulfate, amide, silane, carboxyl, hydroxyl groups are covalently spring the MONPs and deed as a linker between the biomolecules and NPs. For example, Varache et al. conjugated carboxyl groups to mesoporous SiO_two NPs (covalently attached) to bind with PEG or PEI (Varache et al., 2022). Farther, cisplatin was conjugated with PEG or PEI coated SiO_ii NPs and studied the drug release pattern later surface functionalization. The results revealed that PEI-coated SiO₂ NPs were more efficient in delivering cisplatin than PEG-coated SiO₂ NPs. Jaramillo et al. (2017) attempted to surface functionalized ZnO NPs with APTES using the direct mixing method, where ZnO NPs and APTES were mixed for 24 hrs under constant stirring. The surface functionalization was confirmed using FTIR and Raman spectroscopy. The results suggested that APTES was attached on the surface of ZnO NP via one or two Si-O-Zn (covalent bail) bonds.

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Construction of Organic Compounds

Robert J. Ouellette , J. David Rawn , in Principles of Organic Chemistry, 2022

Covalent Bonds

A covalent bail consists of the mutual sharing of one or more than pairs of electrons between two atoms. These electrons are simultaneously attracted by the ii atomic nuclei. A covalent bail forms when the difference between the electronegativities of two atoms is too pocket-size for an electron transfer to occur to class ions. Shared electrons located in the infinite between the two nuclei are called bonding electrons. The bonded pair is the "glue" that holds the atoms together in molecular units.

The hydrogen molecule is the simplest substance having a covalent bond. It forms from ii hydrogen atoms, each with ane electron in a 1s orbital. Both hydrogen atoms share the two electrons in the covalent bond, and each acquires a helium-similar electron configuration.

$\mathrm{H}•+\mathrm{H}•\to \mathrm{H}—\mathrm{H}$

A similar bond forms in Cl₂. The ii chlorine atoms in the chlorine molecule are joined by a shared pair of electrons. Each chlorine atom has seven valence electrons in the third energy level and requires one more electron to form an argon-like electron configuration. Each chlorine atom contributes one electron to the bonding pair shared by the two atoms. The remaining half-dozen valence electrons of each chlorine cantlet are not involved in bonding and are concentrated around their respective atoms. These valence electrons, customarily shown as pairs of electrons, are variously chosen nonbonding electrons, lone pair electrons, or unshared electron pairs.

The covalent bond is drawn as a dash in a Lewis construction to distinguish the bonding pair from the lone pair electrons. Lewis structures evidence the nonbonding electrons as pairs of dots located about the atomic symbols for the atoms. The Lewis structures of four simple organic compounds—methane, methylamine, methanol, and chloromethane—are fatigued here to show both bonding and nonbonding electrons. In these compounds carbon, nitrogen, oxygen, and chlorine atoms accept iv, 3, ii, and one bonds, respectively.

The hydrogen atom and the element of group vii atoms form simply i covalent bond to other atoms in most stable neutral compounds. However, the carbon, oxygen, and nitrogen atoms tin can simultaneously bail to more than one atom. The number of such bonds is the valence of the atom. The valences of carbon, nitrogen, and oxygen are four, 3, and two, respectively.

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Ionic Bonding, Crystals, and Intermolecular Forces

James East. House , Kathleen A. Business firm , in Descriptive Inorganic Chemistry (Third Edition), 2022

4.two.1 Dipole–Dipole Forces

Covalent bonds can have observable polarity due to the unequal sharing of electrons past atoms that take different electronegativities. For near types of bonds, this accuse separation amounts to only a small-scale percent of an electron charge. For example, in HI information technology is virtually 5%, but in HF where the departure in electronegativity is about ane.viii units, information technology is nearly 44%.

In order to prove how dipole–dipole forces arise, let usa consider a polar molecule that can be represented every bit

where δ+ and δ− represent the fraction of an electronic charge residing on the positive and negative ends, respectively. When polar molecules are allowed to approach each other, there volition be an electrostatic interaction betwixt them. The actual energy of the interaction will depend on the orientation of the dipoles with respect to each other. Two limiting cases can be visualized as shown in Effigy four.nine.

Figure 4.ix. Interaction of dipoles by the (a) parallel and (b) antiparallel modes.

Past assuming an averaging of all possible orientations, the energy of interaction, East _D tin be shown to exist

(4.xiii) $E_{\text{D}}=-\frac{2{\mu }^{\mathrm{four}}}{3kT{R}^6}$

where μ is the dipole moment, R is the average altitude of separation, k is Boltzmann'southward constant, and T is the temperature (K). On the basis of this interaction, it is expected that polar molecules should associate to some extent, either in the vapor state or in solvents of low dielectric constant. Dipole association in a solvent having a low dielectric constant leads to an aberrant relationship between the dielectric abiding of the solution and the concentration of the polar species. Although the procedure volition not be shown, it is possible to calculate the clan constants for such systems from the dielectric constants of the solutions. If the solvent has a loftier dielectric constant and is polar, it may solvate the polar solute dipoles thus preventing association which forms aggregates. Consequently, the association constants for polar species in solution are always dependent on the solvent used.

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Basic Coordination Chemical science

Vasishta Bhatt , in Essentials of Coordination Chemical science, 2022

1 Introduction

The coordination compounds found their applications long earlier the institution of coordination chemistry. Bright red coloured alizarin dyes were under applications even before the fifteenth century. This bright red dye, now characterized as a chelated complex of hydroxyanthraquinone with calcium and aluminium metallic ions, is shown in Effigy 1.

Figure 1. Structure of alizarin dye.

Later, in the sixteenth century, the formation of a well-known member of today's coordination chemistry family unit, the tetraamminecupric ion [Cu(NH_three)_iv]⁺ⁱⁱ, was recorded upon contact between brass alloy and ammonium chloride. Addition of Prussian blueish Atomic number 26_iv[Iron(CN)₆]_iii·10H₂O increased the utilize of coordination compounds in dyes and pigments. A platinum complex Thousand_two[PtCl_six] offered an application for the refinement of platinum metallic. Thus, before the coordination chemistry was structured, the coordination compounds, complexes and chelates found their applications.

A systematic investigation of structure and bonding in coordination chemistry began with the inquisitiveness of Tassaert (1798), which was extended by distinguished chemists similar Wilhelm Blomstrand, Jorgensen and Alfred Werner [1] until the finish of the nineteenth century. In the events, Werner's coordination theory (1893) became the base of the modern coordination chemistry. It is worth noting that the electron was discovered subsequent to Werner's theory.

The bonding in compounds like CoCl₃ and NH₃ were easily understood and explained and hence such compounds were regarded as simple compounds. For instance, the +3 formal oxidation of cobalt in cobalt chloride is counterbalanced by 3 uni-negative chloride ions and the coexistence of these ionic moieties to course a molecule is understood and explained. Similarly, the valence shell (n  =   2) of nitrogen (N   =   7) contains five electrons and four orbitals (2s, 2p _x , 2p _y and 2p _z ). Keeping an electron pair in one of these orbitals while the other three remains one-half filled, an opportunity for 3 hydrogen atoms to contribute one electron each for the germination of a covalent bond with nitrogen, tin can besides be explained. Thus an ammonia molecule has three Northward H covalent bonds and one solitary pair of electrons over the nitrogen atom. Information technology is worth noticing here that all the valencies of all the atoms in both the molecules are fully satisfied and hence there is no farther scope of bonding.

A 'complex' state of affairs arises when one comes to know that the molecule CoCl₃ can encompass six ammonia molecules, resulting into a third contained entity. This situation was fully understood and explained past Werner's coordination theory, followed by naming the entity as 'complex'.

one.1 Definitions

Coordination compounds are the compounds containing 1 or more coordinate covalent bonds.

Coordinate covalent bonds are the covalent bonds in which both the bonding electrons are contributed by ane of the bond partners. Figure 2 distinguishes the covalent bonds from the coordinate covalent bail in NH₃BF₃. While the three BF covalent bonds are formed due to the sharing of electron pairs resulting from contributions of both boron and fluorine atoms, an NB bail is formed due to the donation of a solitary pair of electrons from nitrogen into the empty orbitals of boron. The coordinate covalent bond is shown by an arrow with its head pointing towards the management of the donation of an electron pair, as shown in Figure 2.

Figure 2. Bonding in NH_threeBF₃.

A complex is a molecule/ion containing a primal metal cantlet/ion surrounded by a definite number of ligands held by secondary valences or coordinate covalent bonds.

Primary valency refers to the charge over the metal ion e.g. Co(Iii) has +3 accuse, which tin can be balanced by −3 charge-forming compounds similar CoCl₃. The primary valency is ionic and is satisfied in the second coordination sphere, as shown in Figure 3.

Effigy 3. Commencement and second coordination spheres in [Co(NH₃)_{half dozen}]Cl₃.

Secondary valency is the number of empty valence orbitals, equally illustrated for [Co(NH₃)₆]Cl_iii in the figure. The Co(III) ion has six empty valence orbitals. Hence its secondary valency is six. Secondary valency is a coordinate covalent valency, and information technology is satisfied in the first coordination sphere of the metal ion, as shown in Figure 4.

Figure 4. Secondary valency of Co(III) in [Co(NH₃)₆]Cl₃.

Coordination number is a property of the metal ion representing the total number of donor atoms direct fastened to the fundamental atom. In the to a higher place case, the coordination number of Co(3) is vi, equally six nitrogen donor atoms are directly connected to the central metal ion (cobalt(Iii)).

Ligand is any atom, ion or neutral molecule capable of donating an electron pair and bonded to the primal metal ion or atom through secondary valency.

Dentate character is a property of a ligand representing a number of coordinating atoms.

In the instance of [Co(NH₃)₆]Cl_three, ammonia, NH₃ the ligand contains one donor atom (Northward). Hence its dentate character is ane and is classified as a monodentate ligand. Similarly, chloro (Cl⁻) is an anionic, monoatomic and monodentate ligand, while hydroxo (OH⁻) is a diatomic, monodentate and anionic ligand. Aquo (OH₂) represents a neutral triatomic monodentate ligand. A few popular ligands and their characteristics are shown in Figure 5.

Figure 5. Structures and characteristics of a few of import ligands.

Due to a higher dentate character of ligands, a variety of complexes known equally chelate is besides formed sometimes. Chelate is a chemical compound formed when a polydentate ligand uses more than than ane of its analogous atoms to form a closed-ring structure, which includes the central metal ion. Five- and half dozen-membered rings are known to provide extra stability to the chelates. The process of chelate formation is known as chelation. A polydentate ligand involved in chelate formation is also known as a chelating ligand. Chelates generally exhibit higher stability than analogous complexes.

A polydentate ligand may exist fastened to the central metal ion through more than i kind of functional group. The number and kind of linkages by which the metal ion is attached with the ligands can thus become a criterion for the nomenclature of chelates. The covalent bonds are formed by the replacement of i or more H-atoms, while coordinate covalent bonds are formed by the donation of an electron pair from the ligands. Some of the chelates involving a diverseness of polydentate ligands and linkages are shown in Figure six. The coordinate covalent linkages are shown by thin, thread-like bonds.

Figure half dozen. Structures and characteristics of a few chelates.

Polynuclear complex is a complex with more than than one metal atom/ion. These metal ions are sometimes bridged through appropriate ligands, resulting into the formation of a bridged polynuclear circuitous.

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Introduction

Huangxian Ju , ... Feng Yan , in Immunosensing for Detection of Poly peptide Biomarkers, 2022

ane.iii.3 Covalent binding

Covalent bonds are by and large formed between side-chain-exposed functional groups of proteins and suitably modified transducer surface, resulting in an irreversible bounden and producing a high surface coverage [ 71,72]. One of the almost ordinarily used methods for covalent immobilization is to couple the antibody randomly via their gratis amino groups to an activated sensor surface (Fig. 1.5). Chemical coupling agents, such every bit carbodiimides and succinimidyl esters, may be used to actuate carboxylic acids on sensor surfaces. Amines or alcohols can be activated by isothiocyanates, epoxides, glutaraldehyde (GA), or other aldehydes. Oxidation of alcohols is achieved with periodate to yield aldehydes, which react readily with amines. In add-on, conversion of alcohols to a highly reactive ester past cyanogen bromide allows for further reaction with amines of antibody. For example, the ultrasonication treatment of carbon nanotubes (CNTs) in full-bodied acrid condition tin produce abundant carboxyl groups on their surface. When CNTs are modified on the electrode surface, the carbodiimide/North-hydroxysuccinmide system is commonly applied to link antibodies with the activated carboxyl groups [sixty].

Fig. 1.v. Schematic illustration of covalent immobilization of antibodies to sensor surfaces via their free amino groups. Reaction (a) involves activation of carboxylic acids (COOH), accomplished with carbodiimides and succinimyl esters. Reaction (b) shows amine surfaces (NH₂), which tin be activated using isothiocyanates, epoxides, or aldehydes. Reaction (c) shows alcohol surfaces that can exist activated using periodate oxidation, isothiocyanates, epoxides, aldehydes, and cyanogen bromide.

Another approach is to apply bifunctional cross-linking reagents [73]. The cantankerous-linking reagents contain ii different reactive groups, thereby providing a means of covalently linking 2 dissimilar target groups on the sensor surface and poly peptide biomolecules. A broad variety of these linkers such as (3-aminopropyl)triethoxysilane (APTES) [74], (three-glycidoxypropyl)-trimethoxysilane (GPTMS) [75], 3-mercaptopropyltrimethoxysilane (MPTMS) [76], diazonium cation [77], and diverse thiol derivatives [78–80] are commercially available to cover a wide range of functional groups necessary. For instance, the silanization reaction of APTES at the hydroxyl group-containing substrate (east.g., drinking glass, electrode, and microwell plate) can provide amino groups at the surface. Then antibodies can be coupled to the substrate via the cross-linking of GA (Fig. one.6).

Fig. 1.six. Schematic illustration of immobilization of antibiotic by the bifunctional cross-linking reagents of APTES and GA.

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CRYSTAL STRUCTURE OF THE METALLIC ELEMENTS

Due west. STEURER , in Concrete Metallurgy (Quaternary Edition), 1996

2.one.i. The covalent bail

The covalent bail may be described in terms of the more than qualitative VB (valence bond) theory by overlapping atomic orbitals occupied past unpaired valence electrons ( fig. 1). Its strength depends on the degree of overlapping and is given by the exchange integral. In terms of the more quantitative LCAO–MO (linear combination of diminutive orbitals – molecular orbitals) theory, molecular orbitals are synthetic past linear combination of atomic orbitals (fig. two). The resulting bonding, not-bonding and anti-bonding molecular orbitals, filled up with valence electrons co-ordinate to the Pauli exclusion principle, are localized between the bonding atoms with well defined geometry. Generally, covalent bonds can be characterized as strong, directional bonds. Increasing the number of atoms contributing to the bonds increases the number of molecular orbitals and their energy differences get smaller and smaller. Finally, the detached energy levels of the molecular orbitals condense to quasicontinuous bands separated by energy gaps. Since in a covalent bail each atom reaches its particular stable element of group 0 configuration (filled beat out) the energy bands are either completely filled or empty. Owing to the localization of the electrons, information technology needs much energy to lift them from the terminal filled valence band into the empty conduction band. The classic case of a crystal built from just covalently bonded atoms is diamond: all carbon atoms are bonded via tetrahedrally directed sp³ hybrid orbitals (fig. 3). Thus the crystal structure of diamond results equally a framework of tetrahedrally coordinated carbon atoms (fig. four).

Fig. 1. Schematic structure of the atomic s-, p- and d-orbitals

(from Vainshtein et al. [1982]).

Fig. 2. (a) Bonding and (b) anti-bonding molecular orbitals of the H_two molecule, (c) Schematic cartoon of the building of the most of import molecular orbitals from atomic orbitals and (d), (eastward) examples of molecular orbitals (bonding: σ, π and anti-bonding σ*, π*)

(from Vainshtein et al. [1982]).

Fig. iii. Hybridization of (a) one due south- and three p-orbitals to (b) sp³–hybrid orbitals (c) which are directed along tetrahedron axes

(from Vainshtein et al. [1982]).

Fig. four. The structure of diamond cF8–C, infinite grouping Fd $\overline{3}$ m, No. 227, 8a: 0 0 0, ¾ ¼ ¾. All carbon atoms are tetrahedrally coordinated, they occupy the positions of a face-centered cubic lattice and one half of the centers of the eighth cubes.

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Supramolecular Receptors

J. Gawroński , ... U. Rychlewska , in Comprehensive Supramolecular Chemical science II, 2022

Abstruse

Dynamic covalent bond formation between primary amines and aldehydes is the ground of synthesis of macrocyclic imines under thermodynamic equilibrium weather. With the use of chiral vicinal diamines and aromatic di- or trialdehydes, a variety of chiral imine macrocycles or cages tin exist readily obtained with high yields. The imine macrocycles are rigid, while the imine reduction products, oligoamines, are flexible. Triangular [3  +   3] cyclocondensation–reduction products are versatile chiral hexaamines with numerous applications for chiral bigotry in NMR spectroscopy and for asymmetrical catalysis. These and related aza-macrocycles display tendency toward formation of supramolecular complexes.

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