Useful synthetic pathways to original, stable tunable neutral and anionic phosphorus dendrimers: new opportunities to expand dendrimer space

High yield multistep synthesis of stable and diversely functionalized phosphorus dendrimers is reported.

Vibrational spectroscopic investigation of the gold complexation within the cascade structure of phosphorus-containing dendrimer

The interaction of the phosphoric dendrimer with gold was performed by means of vibrational spectroscopy and quantum chemistry. Stable complexes are formed with a PN-PS linkage, whereas with an isolated PS bond this does not occur. The change in geometric parameters and delocalization of electric charge under the influence of gold was discovered. The classification of bands in the experimental vibrational spectra of the dendrimer and its complex was carried out. HOMO of molecule of the dendrimer is localized on the SPNP linkage, whereas the LUMO is located on the terminal group. In the SPNP linkage there is a noticeable delocalization of the charge which leads to a change in the reactivity of this group. Interaction energy was estimated as the difference between the energies of the complex and the energies of the molecules of the dendrimer G'₀ and two molecules AuCl and is equal to 25.2 eV. The ionization energy IE and electron affinity EA for AuCl are higher than for dendrimer, therefore, when the complex is formed, these quantities increases. Chemical potential and the electrophilicity index in the complex also increases.

Vibrational spectroscopic study of cationic phosphorus dendrimers with aminoethylpiperidine terminal groups

Two generations of phosphoric dendrimers with piperidine functional groups were synthesized for use in biology and medicine. Neutral samples are soluble in organic solvents but after protonation these dendrimers become water soluble and can be used for biological experiments. The FTIR and FT Raman spectra of two generations of dendrimers G_i constructed from the cyclotriphosphazene core, repeating units OC₆H₄CHNN(CH₃)P(S)< and aminoethylpiperidine end groups NH(CH₂)₂C₅NH₁₁ were recorded. The study of the IR spectra shows that the NH groups form hydrogen bonds. The calculation of the molecular structure and vibrational spectra of the first generation dendrimer was performed by the method of DFT. This molecule has flat, repeating units and a plane of symmetry passing through the core. The calculation of the distribution of potential energy made it possible to classify the bands in the experimental spectra of dendrimers. Amine groups are manifested in the form of a band of NH stretching vibrations at 3389 cm^-1 in the IR spectrum of G₁. NH⁺ stretching bands located at 2646 and 2540 cm^-1 in the IR spectrum of G₂. The stretching vibrations of NH⁺ groups are noticeably shifted to low frequencies due to the formation of a hydrogen bond with the chlorine atom. The line at 1575 cm^-1 in the Raman spectrum of G₁ is characteristic for repeating units.

Structure, IR and Raman spectra of phosphotrihydrazide studied by DFT

The FTIR and FT Raman measurements of the phosphotrihydrazide (S)P[N(Me)-NH2]3 have been performed. This compound is a zero generation dendrimer G0 with terminal amine groups. Structural optimization and normal mode analysis were obtained for G0 by the density functional theory (DFT). Optimized geometric bond length and angles obtained by DFT show good agreement with experiment. The amine terminal groups are characterized by the well-defined bands at 3321, 3238, 1614cm(-1) in the experimental IR spectrum and by bands at 3327, 3241cm(-1) in the Raman spectrum of G0. The experimental frequencies of asymmetric and symmetric NH2 stretching vibrations of amine group are lower than theoretical values due to intramolecular NH⋯S hydrogen bond. This hydrogen bond is also responsible for higher experimental infrared intensity of these bands as compared with theoretical values. Relying on DFT calculations a complete vibrational assignment is proposed for the studied dendrimer.

Interaction between dendrimers and regulatory proteins. Comparison of effects of carbosilane and carbosilane–viologen–phosphorus dendrimers

For nanoparticles to be used successfully in biomedical application, their interactions with biological fluids need to be investigated, in which they will react with proteins and other macromolecules.

Spectroscopic and molecular structure investigation of the phosphorus-containing G'2 dendrimer with terminal aldehyde groups using DFT method

The FTIR and FT Raman spectra of the second generation dendrimer G'2 built from thiophosphoryl core with terminal aldehyde groups have been recorded. The structural optimization and normal mode analysis were performed for model compound C, consisting of thiophosphoryl core, one branch with three repeated units, and four 4-oxybenzaldehyde terminal groups on the basis of the density functional theory (DFT) at the PBE/TZ2P level. The vibrational frequencies, infrared and Raman intensities for the t,g,g- and t,-g,g-conformers of the terminal groups were calculated. The t,g,g-conformer is 2.0 kcal/mol less stable compared to t,-g,g-conformer. A reliable assignment of the fundamental bands observed in the experimental IR and Raman spectra of dendrimer was achieved. For the low generations (G'1 to G'3) the disk form of studied dendrimer molecules is the most probable. For higher generations, the shape of dendrimer molecules will be that of a cauliflower.

DFT study of Raman spectra of hexakis(4-N'(-di(4-oxyphenethylamino)-(thio)phosphonyl)-N'-methyl-diazobenzene)cyclotriphosphazene

The FT-Raman spectrum of the hexakis(4-N'(-di(4-oxyphenethylamino)-(thio)phosphonyl)-N'-methyl-diazobenzene)cyclotriphosphazene which is the first generation dendrimer G1 built from the cyclotriphosphazene core, six arms -O-C6H4-CH=N-N(CH3)-P(S)< and twelve 4-oxyphenethylamino terminal groups -O-C6H4-(CH2)2-NH2 G1 has been recorded. The structural optimization and normal mode analysis were performed for model compound C, consisting of cyclotriphosphazene core, one arm -O-C6H4-CH=N-N(CH3)-P(S)< and two 4-oxyphenethylamino terminal groups -O-C6H4-(CH2)2-NH2 on the basis of the density functional theory (DFT) at the PBE/TZ2P level. The calculated geometrical parameters and harmonic vibrational frequencies are predicted in good agreement with the experimental data. It was found that G1 has a concave lens structure with planar -O-C6H4-CH=N-N(CH3)-P(S)< fragments and slightly non-planar cyclotriphosphazene core. The 4-oxyphenethylamino groups attached to different arms show significant deviations from a symmetrical arrangement relative to the local planes of repeating units. The experimental Raman spectra of G1 dendron was interpreted by means of potential energy distribution. Relying on DFT calculations, as well as on experimental information, a spectral interpretation was proposed.

Comparative EPR studies of Cu(ii)-conjugated phosphorous-dendrimers in the absence and presence of normal and cancer cells

EPR analysis revealed peculiar structural and dynamical properties of anticancer-activeG3B–Cu(ii) in absence and presence of normal and cancer cells.

Structural and spectroscopic properties of the second generation phosphorus-viologen "molecular asterisk"

The FTIR and FT Raman spectra of the second generation phosphorus-viologen "molecular asterisk" G2 built from cyclotriphosphazene core with 12 viologen units and 6 terminal phosphonate groups have been recorded and analyzed. The experimental X-ray data of 1,1-bis(4-formylbenzyl)-4,4'-bipyridinium bis(hexaflurophosphate) was used in molecular modeling studies. The optimization of isolated 1,1-bis(4-formylbenzyl)-4,4'-bipyridinium (BFBP) molecule without counter ions PF6(-) does not lead to significant changes of dihedral angles, thus the molecular conformation does not depend on interactions with the counter ions. The structural optimization and normal mode analysis were performed for G2 on the basis of the density functional theory (DFT). The calculated geometrical parameters and harmonic vibrational frequencies are predicted in a good agreement with the experimental data. It was found that G2 has a kind of "egg timer" structure with planar OC6H4CHNN(CH3) fragments and slightly non-planar cyclotriphosphazene core. The experimental IR and Raman spectra of G2 were interpreted by means of potential energy distribution.

DFT study of Raman spectra of phosphorus-containing dendrons built from cyclotriphosphazene core with terminal carbamate and ester groups

The FT Raman spectra of the zero (Gv0) and first generations (Gv1) of phosphorus-containing dendrons with terminal carbamate groups and one ester function and [2-(4-hydroxyphenyl)ethyl]-carbamic acid tert-butyl ester (C) have been recorded and analyzed. The lines of free ν(C=O) bonds are not observed in the experimental Raman spectrum of C and thus association of carbamate groups by hydrogen bonds occur. The frequencies of ν(C=O) lines in the experimental Raman spectrum reveal the presence of the different types of H-bonds in the amorphous state of Gv0. Density functional theory (DFT) calculations of C gave geometrical parameters for the t-g-, g-g-, tg-, gg-conformers. The most stable is the gg-conformer. The structural optimization and normal mode analysis were performed for dendrons on the basis of the DFT. The calculated geometrical parameters, harmonic vibrational frequencies and Raman intensities are predicted in a good agreement with the experimental data. The experimental Raman spectra of dendrons were interpreted by means of potential energy distribution. Relying on DFT calculations the lines of a core, repeating units and terminal groups of dendrons were assigned. The polarizabilities and lipophilicity of dendrons were estimated.

Validation of a generation 4 phosphorus-containing polycationic dendrimer for gene delivery against HIV-1

Gene therapy, in which oligomeric genetic material is carried into cells by nano-sized gene delivery vehicles to interfere with gene expression, represents a promising approach for preventive therapy against HIV/AIDS pandemic. Herein, we evaluate the usefulness of a phosphorus-containing dendrimer G4(NH+Et2Cl-)96 as a delivery agent of ODNs and siRNAs. G4(NH+Et2Cl-)96 formed stable complexes with ODNs or siRNAs and exhibited very low cytotoxicity in Sup T1 cells or PBMC. Functional validation was performed by using specific siRNA against HIV-1 Nef, siNEF to interfere in HIV-1 replication. G4(NH+Et2Cl-)96/siNEF dendriplex showed a high efficiency in Nef silencing. Furthermore, in vitro treatment of HIV-infected PBMC with G4(NH+Et2Cl-)96/siNEF dendriplex significantly reduced the viral replication. Our results prove the usefulness of phosphorus-containing dendrimers to deliver and transfect siRNA into CD4-T cells as a potential alternative therapy in the HIV-1 infection.

DFT study of structure, IR and Raman spectra of the first generation dendron built from cyclotriphosphazene core with terminal carbamate and ester groups

The FTIR and FT-Raman spectra of the first generation dendron built from the cyclotriphosphazene core, five arms -O-C(6)H(4)-CH=N-N(CH(3))-P(S) 2 bonds on the righthand side with ten carbamate terminal groups and one ester function G(v1) have been recorded. The IR and Raman spectra of the zero generation dendron G(v0) and first generation dendrimer G(1) with the same core and terminal groups were also examined. The structural optimization and normal mode analysis were performed for dendron G(v1) on the basis of the density functional theory (DFT). The calculated geometrical parameters and harmonic vibrational frequencies are predicted in a good agreement with the experimental data. It was found that G(v1) has a concave lens structure with planar -O-C(6)H(4)-CH=N-N(CH(3))-P(S) 2 bonds on the righhand side fragments and slightly non-planar cyclotriphosphazene core. The carbamate groups attached to different arms show significant deviations from a symmetrical arrangement relative to the local planes of repeating units. The experimental IR spectrum of G(v1) dendron was interpreted by means of potential energy distributions. The strong band 1604 cm(-1) shows marked changes of the optical density in dependence of the carbamate, ester or azomethyne substituents in the aromatic ring. The frequencies of ν(N-H) and ν(C=O) bands in the IR spectra reveal the presence of the different types of H-bonds in the studied dendrimers.

Cytotoxicity and genotoxicity of cationic phosphorus-containing dendrimers

Cationic phosphorus-containing dendrimers (CPDs) are a class of highly-branched polymers with potential medical relevance. However, little is known about CPD modes of interactions with cell and its components, including DNA. In the present work we investigated cytotoxicity and genotoxicity of CPDs generation 3 and 4 (CPD G3 and CPD G4) in human mononuclear blood cells, A549 human cancer cells and human gingival fibroblasts (HGFs). CPD G3 and CPD G4 at concentrations up to 10 μM induced a concentration-dependent decrease in cell viability as assessed by flow cytometry. Both compounds did not induce breaks in isolated DNA as evaluated by the plasmid relaxation assay but they induced DNA cross-links in the cells, as examined by comet assay. CPD G3 and 4 induced slight perturbations in the cell cycle leading to a decrease in the G2/M cell population accompanied by an increase in the S cell population. Upon treatment with CPDs, the cells showed changes in their morphology, including loss of cell attachment, disruption of cell membrane and nucleus condensation. Our results indicate that CPD G3 and G4 are cytotoxic and genotoxic for the assorted human cells. Therefore, CPDs may form stable complexes with DNA and interfere with cellular processes.

Vibrational spectra study of fluorescent dendrimers built from the cyclotriphosphazene core with terminal dansyl and carbamate groups

The FTIR and FT Raman spectra of the "Janus"-type dendrimers, possessing five carbamate groups on one side and five fluorescent dansyl derivatives on the other side, with amide G(1) and hydrazone G(2) central linkages were studied. These surface-block dendrimers are obtained by the coupling of two different dendrons. The FTIR and FT-Raman spectra of the zero generation dendrons, built from the hexafunctional cyclotriphosphazene core, with five dansyl terminal groups and one carbamate G(0v) and one oxybenzaldehyde function G(0v)' have been recorded. The structural optimization and normal mode analysis were performed for dendron G(0v)' on the basis of the density functional theory (DFT). The calculated geometrical parameters and harmonic vibrational frequencies are predicted in a good agreement with the experimental data. It was found that dendron molecule G(0v)' has a concave lens structure with planar -O-C(6)H(4)-CHO fragments and slightly non-planar cyclotriphosphazene core. The experimental IR and Raman spectra of dendron G(0v)' were interpreted by means of potential energy distributions. Relying on DFT calculations a complete vibrational assignment is proposed. The strong band 1597 cm(-1) show marked changes of the optical density in dependence of substituents in the aromatic ring. The frequencies of ν(N-H) bands in the IR spectra reveal the presence of the different types of H-bonds in the dendrimers.

Raman spectroscopy study of phosphorus-containing dendrimers built from thiophosphoryl core

The FT-Raman spectra of 10 generations of phosphorus-containing dendrimers containing P=S and P=O bonds with terminal benzaldehyde and P-Cl groups have been recorded and analyzed. The Raman spectra of dendrimers are determined by the ratio T(n)/R(n) (T(n)--number of terminal groups, R(n)--number of repeating units). This ratio trends to r-1 (r--branching functionality of repeating unit), and becomes constant, when the generation number is higher than 3. The lines full width at half height in Raman spectra of 10 generations was measured. The possibility appears to separate the lines assigned to the core, repeating units and terminal groups of dendrimers by difference spectroscopy method. The influence of the encirclement on the line frequencies and intensities was studied and due to the predictable, controlled and reproducible structure of dendrimers the information, usually inaccessible is obtained. Some lines in the Raman difference spectra have characteristic EPR-like form. The strong line at 1600 cm(-1) show marked changes of intensity in dependence of aldehyde (-CH=O) or azomethyne (-CH=N) substituents in the aromatic ring.

IR spectroscopy investigation using DFT analysis on the structure of P(1) phosphorus dendrimer built from octasubstituted metal-free phthalocyanine core

The IR spectra of P(1) phosphorus dendrimer built from an octasubstituted metal-free phthalocyanine core have been recorded in the region 4000-400cm(-1). Besides the phthalocyanine core, P(1) possess also eight C(6)H(4)-CHN-N(CH(3))-P(S) arms and terminal P-Cl groups. The optimized molecular geometry, frequency and intensity of the IR bands have been calculated using density functional theory (DFT). The P(1) molecules exist in a stable conformation with planar C(6)H(4)-CHN-N(CH(3))- fragments and phthalocyanine core. The calculated geometrical parameters and harmonic vibrational frequencies are predicted in a good agreement with the experimental data. The experimental IR spectrum of P(1) dendrimer was interpreted by means of potential energy distributions. Relying on DFT calculations a complete vibrational assignment is proposed. The difference IR spectra of molecules built from the thiophosphoryl, cyclotriphosphazene, and phthalocyanine cores with the same repeated units and terminal groups were studied in order to undermine the role of the core functionality on the dendrimer architecture.

FTIR and FT-Raman spectra and DFT vibrational analysis of phosphorus-containing dendrons

FTIR and FT-Raman spectra of four generations of phosphorus-containing dendrons with terminal aldehyde or PCl groups have been recorded and analyzed. Their spectral patterns are determined by the ratio T/R (T, the number of terminal groups; R, the number of repeated units). Bands assigned to the core, repeated units and terminal groups were separated by the difference spectroscopy method. The optimized geometry, frequencies and intensity of IR bands of G(1v) generation dendron with terminal aldehyde groups were obtained by the density functional theory (DFT). It was found that the internal skeleton of molecules exists in a single stable conformation with planar O-C(6)H(4)-CHN-N(CH(3))-P(S) fragments, but terminal groups may adopt the t,g,g- and t,-g,g-rotational isomers. The t,-g,g-conformer is 0.74 kcal/mol less stable compared to the t,g,g-conformer. The bond length and bond angles obtained by DFT show the best agreement with experimental data. Relying on DFT calculations a complete assignment of vibrations is proposed for different parts of the studied dendrons. The calculated frequencies and intensity of IR bands of the t,g,g- and t,-g,g-conformers of G(1v) are found to be in reasonable agreement with the experimental results. The most reactive site in dendron is the core function and vinyl group is preferred for nucleophilic attack. In dendrimer the most reactive are the terminal groups.

DFT analysis of structure and IR spectra of phosphorus G1v generation dendron

FT-IR spectra of phosphorus dendron G(1v) generation with terminal P-Cl groups have been recorded. Density functional theory is used for analyzing the properties of each structural part (core, branches, surface). It is found that the repeating branching units of G(1v) exist in a single stable conformation with planar -O-C(6)H(4)-CH=N-N(CH(3))-P fragments. DFT results for the structure of G(1v) are in good agreement with recent X-ray diffraction measurements. A complete vibrational assignment is proposed for different parts of G(1v). The global and local reactivity descriptors have been used to characterize the reactivity pattern of the core function and terminal group. Our study reveals that the most reactive site of G(1v) is the core function and =CH(2) side of vinyl group is preferred for nucleophilic attack. In the dendrimer G(1) the most reactive are the terminal groups. IR spectroscopy combined with ab initio DFT computation provides unique detailed information about the structure and reactivity of the technologically relevant materials, which could not be obtained before with any other technique.

DFT calculations of structure and IR spectra of the phoshorus-containing G'0v generation dendron

FT-IR spectra of the phosphorus-containing dendron G'(0v) generation with terminal aldehyde groups have been recorded. The structural optimization and normal mode analysis are performed for the G'(0v) on the basis of the ab initio density functional theory. This calculations gave vibrational frequencies and infrared intensities for the t,g,g- and t,-g,g-conformers of the G'(0v). The t,-g,g-conformer is 0.71 kcal/mol less stable compared to t,g,g-conformer. Relying on DFT calculations a complete vibrational assignment is proposed for different parts of the dendron. The influence of encirclement on band frequencies and intensity is studied and the information usually inaccessible is obtained. The global and local reactivity descriptors have been used to characterize the reactivity pattern of the core function and terminal groups. Our study reveals that the most reactive site in the dendron is the core function and the CH(2) side of the vinyl group is preferred for nucleophilic attack. In the dendrimer the most reactive are the terminal groups.

Fourier-transform infrared and Raman difference spectroscopy studies of the phosphorus-containing dendrimers

FT IR and Raman spectra of 12 generations of the phosphorus-containing starburst dendrimers containing P=S and P=O bonds with terminal aldehyde and P-Cl groups were compared. The influence of the encirclement on the band frequencies and intensity is studied and due to the predictable, controlled and reproducible structure of the dendrimers the information usually inaccessible is obtained. Bands in the IR difference (G2'(P=O)-G2'(P=S)) spectra have characteristic EPR-like form. The strong band at 1600 cm(-1) show marked changes of the optical density in dependence of the aldehyde (-CH=O) or azomethyne (-CH=N-) substituents in the aromatic ring. The analysis of difference spectra enables one to assign the characteristic bands nu(P=S) and nu(P=O) for the bonds in the core, in the repeating unit and in the terminal groups of the dendrimers. This assignment is supported by the calculation of the absorption curves of the different fragments of dendrimer with the force constants and electro-optical parameters. The IR and Raman spectra of dendrimers are depended on the ratio of number terminal groups to a number of repeating units, which in its turn is strictly determined by the generation number. Thus, the marked differences in the vibrational spectra of the first successive generations aspire to zero for the higher ones. The rather rigid repeated units with little conformational flexibility define the perfect microstructure of the studied phosphorus-containing dendrimers up to the eleventh generation.

Calculation of IR spectra of the elementoorganic dendrimers

Various approximations to the analysis of the dendrimer vibrational spectra are introduced. The merits and demerits of the fragment method, calculation of the first generation and linear chains containing different number of the repeated units are discussed. The experimental spectra of two series of the phosphorus-containing starburst dendrimer generations are interpreted on the basis of the calculation of the frequencies of the normal vibrations and the band intensities in their IR spectra. The analysis of spectra enables one to assign the characteristic bands for the groups in the core, in the repeating unit and the terminal groups of the dendrimers. This assignment is supported by the calculation of the absorption curves with the force constants and electro-optical parameters (EOP). The vibrational spectra of studied starburst dendrimers (SD) (up to 11 generations) are in general identical to begin with four generation. The most marked changes of band position and their intensities are seen in spectra of the first generations, when all fragments of molecule contribute appreciably to the spectral pattern. The comparative study of vibrational spectra of SD and linear polymers reveal their main characteristic features, which are determined by their structural peculiarities.

Synthesis and characterization of linear, hyperbranched, and dendrimer-like polymers constituted of the same repeating unit

The synthesis of a linear polymer that includes both P=N and P=S double bonds, and P-O and P-C single bonds is reported by using two different paths that involve deprotection reactions and the Staudinger reaction. The preparation of hyperbranched polymers made up of OC6H4P(Ph)2=N-P=S repeating units is also described. Five generations of dendrimers originating from the same building blocks were prepared. The characterisation of all these phosphorus-based macromolecular architectures (solution behaviour, size exclusion chromatography, intrinsic viscosity, thermal behaviour) revealed marked differences in their respective behaviour.

X-H (X = C, N, O, P, S) bond activations induced by beta-heterosubstituted zirconaindenes

The azazirconacyclopentene-substituted phosphines 3 and 4 have been found to activate the C-H bonds of acetylenic systems, such as methylpropiolate, diphenylphosphinoacetylene and phenylacetylene, or of methylene compounds, such as malonitrile and diethylmalonate, to give complexes 5a-c, 6a and 6b. C-H bond activation also takes place with vinylacetate. Similar reactions with amines, alcohols, enolisable ketones, phenols, phosphonates, thiols and a second-generation SH-terminated dendrimer lead through X-H bond activation (X = N, O, P, S) to new complexes 8a-c, 9, 12 a,b, 13, 14a-c, 15, 16a and 16b. The azazirconacyclopentene-substituted amine 20 reacts to form analogous complexes. Zr-X bonds of these complexes (X = C, N, O, S) can be cleaved with diphenylchlorophosphine to give P-X phosphorus derivatives in high yield.

Naked Au55 clusters: dramatic effect of a thiol-terminated dendrimer

Reaction of the thiol-terminated fourth-generation dendrimer 2-G4 (96 SH groups) with the gold cluster compound Au55(PPh3)12Cl6 in a 3:1 molar ratio in dichloromethane results in the formation of bare Au55 clusters. The cuboctahedrally shaped Au55 particles coalesce to well-formed microcrystals (Au55) infinity. The role of the dendrimer is not only to remove the phosphine and chlorine ligands but also to act as an ideal matrix for perfect crystal growth. Transmission electron microscopy (TEM), small- and wide-angle X-ray diffraction (SAXRD and WAXRD) measurements indicate a structure where rows of edge-linked Au55 building blocks form a distorted cubic lattice. The X-ray data fit best if a 5% reduction of the Au-Au bond length in the Au55 clusters is assumed, in agreement with previous extended X-ray absorption fine structure (EXAFS) measurements. Energy-dispersive X-ray spectroscopy (EDX) analyses and IR investigations show the absence of PPh3 and Cl in the microcrystals.

Unexpected formal [1+3] cycloadditions between azides and alpha-zirconated phosphanes: a route to unprecedented phosphazide and iminophosphorane complexes

Polycyclic zwitterionic complexes that incorporate one or two phosphonium unit(s) as cationic center(s) and zirconocene-ate moiety(ies) as the anionic counterpart(s) can be easily prepared by either [1+3] or [1+3] and [2+3] cycloadditions which involve bi- or tricyclic alpha-zirconated phosphanes 3 or 4 and various azides. Some of these species exhibit unprecedented phosphazide chelation with bonding between the zirconium and a nitrogen atom in the alpha position relative to phosphorus. When heated, the phosphazide complexes lose dinitrogen to form stable polycyclic zwitterionic phosphonium mono- or dinuclear complexes. The solid-state structure of the two zwitterionic complexes 5 and 8 was determined by X-ray crystallography.