Central Zn Atom Research Articles

Ethylenediamine control of the solid-state supramolecular chemistry of zinc phthalocyanine

The two axially ligated H-shaped and T-shaped zinc phthalocyanine derivatives, ZnPc(EDA)ZnPc and ZnPc(EDA), were obtained directly by thermal reaction of ZnPc in ethylenediamine (EDA) solution. Both complexes, ZnPc(EDA)ZnPc and ZnPc(EDA), co-crystallize with the EDA and water molecules yielding good-quality single crystals [ZnPc(EDA)ZnPc][ZnPc(EDA)]2∙2EDA·6H2O − 1. The interaction of Zn center of ZnPc with the axial substituent containing lone electron pair on NH2 groups with zinc phthalocyanine in both zinc phthalocyanine derivatives, ZnPc(EDA)ZnPc and ZnPc(EDA), leads to a deviation of Zn from the centre of cavity by 0.442(3) and 0.514(3) Å in the T- and H-shaped molecules as well as causes, as expected, the deformation of the planar molecule ZnPc into a saucer-shape conformation. Thus, in both types of molecules the central Zn atom of ZnPc complexes with EDA molecule exhibits 4 + 1 coordination formed by the four isoindole nitrogen atoms of the Pc macrocycle at the equatorial position and the nitrogen atom of the amino group of the EDA molecule at the axial position. Supramolecular arrangement of the T-shaped and H-shaped ZnPc-derivatives in crystal is characterized by a reduction of π···π interactions and an improvement in inter-system crossing in relation to parent ZnPc, and is controlled by the NH∙∙∙O, NH∙∙∙N and OH∙∙∙O hydrogen bonds formed between the T- and H-shaped molecules and lattice EDA and water molecules, which results in increase its solubility and improved photophysical and photochemical properties. The aggregation behaviour of T- and H-shaped ZnPc derivatives building crystals 1 in solutions was investigated by UV–Vis spectroscopy. In order to support and verify the experimental results, the DFT and time-dependent (TD) DFT calculations were performed.

Experimental and Theoretical Survey of Intramolecular Spodium Bonds/σ/π-Holes and Noncovalent Interactions in Trinuclear Zn(II)-Salen Type Complex with OCN- Ions: A Holistic View in Crystal Engineering.

In this work, one new centrosymmetric trinuclear Zn(II) complex 1, [{(OCN)Zn(L)}2Zn], using a salen-type ligand (H2L) in the presence of OCN- was synthesized and characterized via elemental, spectral, SEM-EDX, and single-crystal X-ray diffraction (SCXRD) study. In 1, SCXRD reveals two different stereochemical environments of zinc metal ions; one terminal Zn(II) center adopts square pyramidal geometries with the Addison parameter (τ) 0.095, and the central Zn(II) is tetracoordinated tetrahedral geometry. This article provides evidence of the significance and presence of spodium bonds (SpBs) in solid-state crystal structures involving a pseudotetrahedral environment of the central Zn-atom. X-ray structures reveal intramolecular Zn···O SpBs caused by the methoxy (-OCH3) substituent O-atom adjacent to the coordinated phenoxy O-atom. These noncovalent interactions have been thoroughly studied using density functional theory calculations at the RI-BP86[2]-D3[3]/def2-TZVP level of theory that characterizes the nature of SpBs, including the Baders quantum theory of atoms-in-molecules "QTAIM", molecular electrostatic potential (MEP) surface, and noncovalent index plot (NCI). In addition, a unique complex-isomer-based theoretical model has been vividly employed to estimate the SpBs energy in the complex. Natural bond orbital (NBO) analysis also tries to establish the differentiation between σ-hole and π-hole SpBs' natures more authentically. The complex energy frameworks were used to investigate noncovalent interactions. To better understand the different intermolecular interactions, we conducted a Hirshfeld surface, which revealed N···H (15.4%) and O···H (9.1%) contacts and Zn···O (5.1%) (SpBs).

Current-Density Calculations on Zn-Porphyrin40 Nanorings.

Two porphyrinoid nanorings have been studied computationally. They were built by linking 40 Zn-porphyrin units with butadiyne bridges. The molecular structures belonging to the D40h point group were fully optimized with the Turbomole program at the density functional theory (DFT) level using the B3LYP functional and the def2-SVP basis sets. The aromatic character was studied at the DFT level by calculating the magnetically induced current-density (MICD) susceptibility using the GIMIC program. The neutral molecules are globally non-aromatic with aromatic Zn-porphyrin units. Charged nanorings could not be studied because almost degenerate frontier orbitals led to vanishing optical gaps for the cations. Since DFT calculations of the MICD are computationally expensive, we also calculated the MICD using three pseudo-π models. Appropriate pseudo-π models were constructed by removing the outer hydrogen atoms and replacing all carbon and nitrogen atoms with hydrogen atoms. The central Zn atom was either replaced with a beryllium atom or with two inner hydrogen atoms. Calculations with the computationally inexpensive pseudo-π models yielded qualitatively the same magnetic response as obtained in the all-electron calculations.

Zn, O Co-adsorption based on MOF-5 for efficient capture of radioactive iodine

The harmful effects of iodine in nuclear waste gas on humans and the environment, as well as the high kinetic energy of iodine molecules caused by the high-temperature environment, make it very important to develop and produce adsorbents with many active sites. The performance and mechanism of iodine capture by MOF-5 were investigated by experiments and molecular simulations for environmental protection. It was found that the synthesized MOF-5 can remove iodine from the gas phase and cyclohexane solution, with a high iodine capture capacity (0.63 g g-1) at 75 ℃. The cycling test illustrated the better recoverability and stability of MOF-5. The iodine capture capacity of MOF-5 in the liquid phase was 155 mg g-1, which is not the same as that of iodine in the gas phase. The multi-scale mechanistic analysis revealed that the adsorption process of MOF-5 on iodine was dominated by chemisorption, and the efficient capture of iodine was achieved by the co-adsorption of the central metal Zn atom and the tetrahedral apex O atom of MOF-5. This study provides insight into the iodine trapping process and adsorption mechanism, which is instructive for environmental protection engineering.

Zinc(II) niflumato complex with neocuproine: Synthesis, crystal structure, characterization and cytotoxic effects on human endometrial cell lines

Novel zinc niflumato complex with a composition of [Zn(neo)(nif)2] (neo = neocuproine; nif = niflumato) was prepared in crystalline form and characterized by elemental analysis and spectroscopic methods (IR, UV/VIS and fluorescence). According to the results of the single-crystal X-ray structural analysis the central Zn(II) atoms within the complex molecules are tetracoordinated by two oxygen atoms of nif ligands and two nitrogen atoms of chelate bonded neo. The cytotoxic measurements on two endometrial cell lines hTERT and 12Z indicate selectivity of the complex towards the endometriotic 12Z cell line. In addition, spectral binding studies performed on isolated DNA samples revealed higher affinity of the complex to the 12Z DNA, thus suggesting possible specific DNA sequence recognition.

Copper(II) and Zinc(II) Complexes Derived from N,N’-Bis(4-bromosalicylidene)propane-1,3-diamine: Syntheses, Crystal Structures and Antimicrobial Activity

A mononuclear copper(II) complex, [CuL] (1), and a phenolato-bridged trinuclear zinc(II) complex, [Zn3Cl2L2(DMF)2] (2), where L is the deprotonated form of N,N'-bis(4-bromosalicylidene)propane-1,3-diamine (H2L), have been prepared and characterized by elemental analyses, IR and UV-Vis spectroscopy, and single crystal X-ray diffraction. The Cu atom in complex 1 is in square planar coordination, while the terminal and central Zn atoms in complex 2 are in square pyramidal and octahedral coordination, respectively. The antibacterial activities of the complexes have been tested on the bacteria Staphylococcus aureus and Escherichia coli, and the yeast Candida parapsilosis.

Synthesis, crystal structure, and spectroscopic properties of bis(rac-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane)(μ-1,2,3,4-oxalato)dichloridozincate(II)(μ-1,2,3-oxalato)dichromium(III) tetrachloridozincate monohydrate

A novel oxalato-bridged trinuclear heterometallic complex, cis-[Cr(cyc b)(μ-1,2,3,4-ox)ZnCl2(μ-1,2,3-ox)Cr(cyc b)]ZnCl4·H2O (1) (cyc b = rac-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane; C16H36N4, ox = oxalate; C2O42−), was prepared and its structure was determined by single-crystal X-ray diffraction analysis at 100 K. Complex 1 crystallizes in the orthorhombic system space group Pca21, with a = 31.702(6), b = 9.087(2), c = 17.677(4) Å, and Z = 4. The two [Cr(cyc b)]3+ units are bridged by the central Zn(II) atom through the oxalato groups, which present bis-bidentate (μ-1,2,3,4-ox) and bidentate-monodentate (μ-1,2,3-ox) modes. Each Cr(III) ion is coordinated by four N atoms from the cyc b ligand and two O atoms of the oxalato ligand in cis-V conformation. The central Zn(II) ion is coordinated in a distorted trigonal-bipyramidal geometry formed by two Cl atoms and two O atoms from μ-1,2,3,4-ox and one O atom from μ-1,2,3-ox. However, the ZnCl42− anion and the uncoordinated water molecule remain outside the coordination sphere. Infrared, UV–visible, and electron paramagnetic resonance spectroscopic analyses confirmed the structural data.

All-Metallic Zn=Zn Double-π Bonded Octahedral Zn2 M4 (M=Li, Na) Clusters with Negative Oxidation State of Zinc.

Zn=Zn double bonded-especially double-π bonded-systems are scarce due to strong Coulomb repulsion caused by the Zn atom's internally crowded d electrons and very high energy of the virtual π orbitals in Zn2 fragments. It is also rare for Zn atoms to exhibit negative oxidation states within reported Zn-Zn bonded complexes. Herein, we report Zn=Zn double-π bonded octahedral clusters Zn2 M4 (M=Li, Na) bridged by four alkali metal ligands, in which the central Zn atom is in a negative oxidation state. Especially in D4h -Zn2 Na4 , the natural population analysis shows that the charge of the Zn atom reaches up to -0.89 |e| (-1.11 |e| for AIM charge). Although this cooperation inevitably increases the repulsion between two Zn atoms, the introduction of the s1 -type ligands results in occupation of degenerated π orbitals and the electrons being delocalized over the whole octahedral framework as well, in turn stabilizing the octahedral molecular structure. This study demonstrates that maintaining the degeneracy of the π orbitals and introducing electrons from equatorial plane are effective means to construct double-π bonds between transitional metals.

The inhibitory effect of the amino acid complexes of Zn(II) on the growth of Aspergillus flavus and aflatoxin B1 production

The zinc(II) complexes with amino acids as the ligands, Zn(Gln)2 (1), [Zn(Arg)2(OAc)]OAc·3H2O (2), Zn(His)2 (3), Zn(Gly)2 (4), Zn(Met)2 (5), and Zn(Cys)2 (6) (Gln = glutamine, Arg = arginine, His = histidine, Gly = glycine, Met = methionine, and Cys = cysteine) have been synthesized in aqueous solutions and characterized by elemental analysis and spectroscopic methods. In addition, the solid-state structure of 1 and 2 has been determined by single-crystal X-ray crystallography. X-ray analysis revealed that the central Zn(II) atom is six- and five- coordinated in 1 and 2, respectively. Furthermore, the antifungal activity of the synthesized complexes was investigated against the Aspergillus flavus fungus. The aqueous solutions of the zinc(II) amino acid complexes at various concentrations were added to the potato dextrose agar (PDA) medium containing spores of Aspergillus flavus, and the mixtures were then incubated at 25–30 °C for 6 days. The aflatoxin B1 produced in vitro was measured using enzyme-linked immunosorbent assay (ELISA). The increasing concentration of these complexes decreased the growth of Aspergillus flavus and aflatoxin B1 production, consequently. Furthermore, the results showed that the synthesized Zn(II) amino acid complexes are more antifungal active than the zinc(II) ion.

In-plane positional correlations among dopants in 10H type long period stacking ordered Mg75Zn10Y15 alloy studied by X-ray fluorescence holography

The local in-plane atomic configuration around Zn in the 10H type long period stacking ordered Mg75Zn10Y15 alloy was investigated using X-ray fluorescence holography. Clear atomic images were observed at 4.2 Å from the central Zn atom, which evidences the robustness of the L12-type Zn6Y8 clusters. On the other hand, atomic images corresponding to the Zn atoms in the adjacent L12 clusters were very weak, suggesting weak inter-cluster positional correlations. A simulation including inter-cluster positional fluctuations with the magnitude of 0.33 Å well reproduced the experimental results.

Tetranuclear Zn(II) and Mononuclear Nickel(II) Complexes Based on Asymmetric Salamo-Type Ligands: Syntheses, Crystal Structures, and Fluorescent Properties

Two new complexes [{Zn(L1)(μ-OAc)Zn(CH3CHOHCH3)}2] and [Ni(L2)(H2O)(CH3OH)] with asymmetric Salamo-type ligands (H3L1 and H2L2) are synthesized and structurally characterized. In the Zn(II) and Ni(II) complexes, the terminal and central Zn(II) atoms are found to have slightly distorted square pyramidal and trigonal bipyramidal symmetries respectively, while the Ni(II) atom is hexa-coordinated and has a slightly distorted octahedral symmetry. Interestingly, a self-assembling continual zigzag 1D chain is formed by intermolecular hydrogen bonds in the Ni(II) complex. Furthermore, the Zn(II) and Ni(II) complexes in the ethanol solution show intense photoluminescence.

Synthesis, crystal structures, spectral, thermal and antimicrobial properties of new Zn(II) 5-iodo- and 5-bromosalicylates

Two new analogous zinc(II) complexes containing 5-iodo- and 5-bromosalicylate ligands, respectively, were prepared in single-crystal form and characterized by IR spectroscopy, thermal analysis and elemental analysis. The solid-state structures of prepared complexes were determined by single crystal X-ray crystallography. Both complexes are isostructural and their crystal structures composed of neutral molecules [Zn(5-Xsal)2(H2O)2] (where X = Br, I, sal = salicylato). Central Zn(II) atom is in both complexes coordinated by six oxygen atoms, four of which are from two chelate bonded 5-halosalicylates and remaining two from coordinated water molecules. The found chelate binding mode is in line with the Δ values calculated from IR spectral data. Antimicrobial activity of prepared complexes was studied against selected bacteria, yeast and filamentous fungi. Obtained results indicate that 5-iodosalicylate complex is more antimicrobially active than its 5-bromo substituted analogue.

Crystal structure of an unknown solvate of (piperazine-κN){5,10,15,20-tetra-kis-[4-(benzo-yloxy)phen-yl]porphyrinato-κ(4) N}zinc.

The title compound, [Zn(C72H44N4O8)(C4H10N2)] or [Zn(TPBP)(pipz] (where TPBP and pipz are 5,10,15,20-tetra-kis-[4-(benzo-yloxy)phen-yl]porphyrinato and piperazine ligands respectively), features a distorted square-pyramidal coordin-ation geometry about the central Zn(II) atom. This central atom is chelated by the four N atoms of the porphyrinate anion and further coordinated by a nitro-gen atom of the piperazine axial ligand, which adopts a chair confirmation. The average Zn-N(pyrrole) bond length is 2.078 (7) Å and the Zn- N(pipz) bond length is 2.1274 (19) Å. The zinc cation is displaced by 0.4365 (4) Å from the N4C20 mean plane of the porphyrinate anion toward the piperazine axial ligand. This porphyrinate macrocycle exhibits major saddle and moderate ruffling deformations. In the crystal, the supra-molecular structure is made by parallel pairs of layers along (100), with an inter-layer distance of 4.100 Å while the distance between two pairs of layers is 4.047 Å. A region of electron density was treated with the SQUEEZE [Spek (2015 ▸). Acta Cryst. C71, 9-18] procedure in PLATON following unsuccessful attempts to model it as being part of disordered n-hexane solvent and water mol-ecules. The given chemical formula and other crystal data do not take into account these solvent mol-ecules.

Syntheses, Crystal Structures, and Thermal Expansion Properties of Three‐Dimensional Cyanide‐Bridged Compounds Zn(4, 4′‐bpy)(H2O)2M(CN)4 (4, 4′‐bpy = 4, 4′‐bipyridine; M = Ni, Pd, Pt)

AbstractAbstract. Three cyanide‐bridged compounds Zn(4, 4′‐bpy)(H2O)2M(CN)4 (4, 4′‐bpy = 4, 4′‐bipyridine; M = Ni (1), Pd (2), Pt (3)) were synthesized by self‐assembly of Zn2+ ions, pillar ligands 4, 4′‐bpy and [M(CN)4]2–. Single‐crystal X‐ray diffraction analysis revealed that compounds 1–3 are isostructural and belong to monoclinic space group C2/c. The zinc atom is located in a distorted octahedral arrangement, whereas the central nickel atom adopts square‐planar arrangement. The central Zn and Ni atoms are linked alternatingly through two cis cyanide groups, generating zigzag chains. The adjacent chains are further connected along two different directions by 4, 4′‐bpy ligands to form a three‐dimensional framework. Thermal expansion (TE) analyses of compounds 1–3 showed that both a and c axes are positive TE coefficients, compared to the near zero TE one along the b axis.

Two new zinc(II) acetates with 3- and 4-aminopyridine: syntheses and structural properties.

The synthesis and characterization of two new zinc(II) coordination compounds with 3- and 4-aminopyridine are reported. They were obtained after adding a water solution of Zn(CH3COO)2·2H2O or dissolving solid Zn(CH3COO)2 ∙ 2H2O in methanol solutions of 3- and 4-aminopyridine. The products were characterized structurally by single-crystal X-ray diffraction analysis. Colourless crystals of the compound synthesized by the reaction of Zn(CH3COO)2·2H2O and 3-aminopyridine (3-apy), are built of trinuclear complex molecules with the formula [Zn3(O2CCH3)6(3-apy)2(H2O)2] (1). The molecules consists of two terminal Zn atoms, coordinated tetrahedrally, and one central Zn atom, coordinated octahedrally. Colourless crystals, obtained by the reaction of Zn(CH3COO)2·2H2O with 4-aminopyridine (4-apy), consist of a mononuclear complex [Zn(O2CCH3)2(4-apy)2] (2). Hydrogen‒bonding interactions in the crystal structures of both complexes are reported.

Crystal structure of di-chlorido-bis-(1,3-diisopropyl-4,5-dimethyl-2H-imidazole-2-thione-κS)zinc(II).

The mol­ecular structure of the title compound, [ZnCl2(C11H20N2S)2], shows tetra­hedral Zn coordination from two Cl ligands and two thione groups. The Zn—Cl bond lengths differ sligthly at 2.2310 (10) and 2.2396 (11) Å while the Zn—S bond lengths are equal at 2.3663 (9) and 2.3701 (10) Å. The Cl—Zn—Cl angle is 116.04 (4) and S—Zn—S is 101.98 (3)°. All other angles at the central Zn atom range from 108.108 (3) to 110.21 (4)°. The C—S—Zn angles are 100.75 (10) and 103.68 (11)°, the difference most probably resulting from packing effects, as both the C—S and both the S—Zn bonds are equal in each case. The two imidazole ring planes make a dihedral angle of 67.9 (1)°. The CH3 groups of one isopropyl moiety are disordered over two sets of sites with occupation factors of 0.567 (15) and 0.433 (15). It may be noteworthy that the isomolecular Cu complex shows a different crystal packing (group–subgroup relation) with the Cu atom lying on a twofold rotation axis. In the crystal, the shortest non-bonding contact is a C—H⋯Cl inter­action. This leads to the formation of centrosymmetric dimers that are stacked along the c-axis.

Isolation of Two Different Ni2Zn Complexes with an Unprecedented Cocrystal Formed by One of Them and a “Coordination Positional Isomer” of the Other

A new homometallic trinuclear Ni(II) complex [(NiL)2Ni(NCS)2] (1) and three heterometallic trinuclear Ni(II)-Zn(II)-Ni(II) complexes [(NiL)2Zn(NCS)2] (2), [(NiL)2Zn(NCS)2(CH3OH)2]·2CH3OH (3) and {[(NiL)2Zn(NCS)2(CH3OH)2]} {[(NiL)2Zn(NCS)2]} (4) have been synthesized by using the "complex as ligand" approach with the "metalloligand" [NiL] (H2L = N,N'-bis(salicylidene)-1,3-propanediamine) and thiocyanate in different ratios. All the complexes have been structurally and magnetically characterized. In the isomorphous complexes 1 and 2, the two terminal square planar Ni atoms and the central octahedral nickel atom (in 1) or zinc atom (in 2) are arranged in a bent structure where two cis κN-SCN(-) thiocyanate ions are coordinated to the central atom. The chemical composition of 3 is very similar to that of 2 but, in 3, the central Zn atom is tetrahedral and the κN-SCN(-) thiocyanate ions occupy an axial position of each terminal nickel atom (which now are octahedral with the sixth position occupied by a methanol molecule). Complex 4 consists of two closely related trinuclear units 4A and 4B. In 4A, the coordination environments of the metals are identical to those of 3 whereas 4B is a "coordination position isomer" of complex 2 with the central square pyramidal Zn and one of the terminal square pyramidal Ni atoms coordinated by two κN-SCN(-) thiocyanate ions. Complex 4 is a unique example of a cocrystal formed by two similar trinuclear units (4A and 4B) where 4A is identical to an existing complex (3) and 4B is a "coordination position isomer" of another existing complex (2).

A new trinuclear zinc(II) complex and a heptacoordinated mononuclear cadmium(II) complex with a pyrimidine derived Schiff base ligand: Syntheses, crystal structures, photoluminescence and DFT calculations

The new N6 donor hexadentate Schiff base 2,4-bis [2-(pyridine-2-ylmethylidene) hydrazinyl] pyrimidine (L), its trinuclear Zn(II) complex, [Zn3(L)2Cl6] (1) and mononuclear heptacoordinate Cd(II) complex [Cd(L)(H2O)2](ClO4)2 (2) have been synthesised and characterised by crystallographically and spectroscopically. Complex 1 is featured by the triangular arrangement of three zinc atoms where the neighbouring Zn atoms are linked via half portion (N3 chromophore) of the same ligand molecule. In 1, the ligand molecules behave as hexadentate ones (employing both pyrimidine nitrogen atoms as active donor centres) to create the octahedral environment around Zn(II). The central and terminal Zn(II) atom has N6 and N3Cl3 chromophores respectively. In 2 the same ligand (L) behaves as pentadentate one (ignoring one pyrimidine nitrogen in the coordination process) to produce a pentagonal bipyramidal geometry with two apical water molecules. The geometries of both complexes were optimised in the singlet state by DFT method. The TDDFT calculations have been done on the optimised geometries to understand the electronic structure and spectral transition in the complexes. Complex 1 exhibits intraligand 1(π→π*) fluorescence in aqueous methanol solvent at room temperature.

Molecular distortion and charge transfer effects in ZnPc/Cu(111)

The adsorption geometry and electronic properties of a zinc-phthalocyanine molecule on a Cu(111) substrate are studied by density functional theory. In agreement with experiment, we find remarkable distortions of the molecule, mainly as the central Zn atom tends towards the substrate to minimize the Zn-Cu distance. As a consequence, the Zn-N chemical bonding and energy levels of the molecule are significantly modified. However, charge transfer induces metallic states on the molecule and therefore is more important for the ZnPc/Cu(111) system than the structural distortions.

Hapticity Uncovered: Real‐Space Bonding Indicators for Zincocene Chemistry

The connectivities (hapticities) of asymmetric cyclopentadienyl zinc compounds are determined by theoretically obtained real-space bonding descriptors. The methods employed herein include the determination of the number of virial paths and electron localizability indicator (ELI-D) basins exhibited between the central Zn atom and the atoms of the ring system. Metal-ring interactions are characterized by flat electron densities and small density gradients, which are related to the high fluxionality of the rings. Due to this, the structures are topologically unstable and the conventional bond-path analysis within the atoms in molecules (AIM) scheme, which in principle can also be applied for experimental electron densities reconstructed from high-resolution X-ray diffraction data, is not a reliable tool for the determination of the hapticity. As a consequence, the theoretical investigation of other real-space bonding descriptors is the necessary primary step for discovering bonding modes that can be applied to molecular geometries obtained by subsequent experiments. By this procedure the common geometrical interpretation of connectivities, which is based on rather arbitrary decisions, is complemented by a self-consistent method using electronic descriptors. Moreover, the two-center σ contributions of all possible bonding scenarios (η(1)-η(5)) were quantified by analyzing the electron populations of the Zn-C σ-bonding basins from the ELI-D analysis inside the AIM Zn atom in relation to the corresponding populations of the C-C π basins of the unsaturated rings. The investigation of the Zn-ring interactions is extended to the delocalization index, the source function, and a new type of electron-density-based surfaces, which we introduce here (ASF = aspherical stockholder fragments). They can be used for visualization of single atoms, fragments (e.g., functional groups), and whole molecules and are based on Hirshfeld's idea of stockholder partitioning, but apply aspherical electron densities. With these surfaces the charge accumulation between the chosen fragments and the steric accessibility of the central Zn atoms become visible, which is a useful tool for explaining and predicting chemical reactivity.