New Liquid Crystalline Materials Based on Two Generations of Dendronised Cyclophosphazenes

Abstract

A divergent approach was used for the synthesis of dendritic structures based on a cyclotriphosphazene core with 12 or 24 hydroxyl groups, by starting from [N(3)P(3)(OC(6)H(4)OH-4)(6)] and using an acetal-protected 2,2-di(hydroxymethyl)propionic anhydride as the acylating agent. Hydroxyl groups in these first- and second-generation dendrimers, G1-(OH)(12) or G2-(OH)(24), were then condensed in turn with mono- or polycatenar pro-mesogenic acids to study their ability to promote self-assembly into liquid crystalline structures. Reactions were monitored by using (31)P{(1)H} and (1)H NMR spectroscopy and the chemical structure of the resulting materials was confirmed by using different spectroscopic techniques and mass spectrometry (MALDI-TOF MS). The results were in accordance with monodisperse, fully functionalised cyclotriphosphazene dendrimers. Thermal and liquid crystalline properties were studied by using optical microscopy, differential scanning calorimetry and X-ray diffraction. The dendrimer with 12 4-pentylbiphenyl mesogenic units gives rise to columnar rectangular organisation, whereas the one with 24 pentylbiphenyl units does not exhibit mesomorphic behaviour. In the case of materials that contain polycatenar pro-mesogenic units with two aromatic rings (A4 vs. A5), the incorporation of a short flexible spacer connected to the periphery of the dendron (acid A5) was needed to achieve mesomorphic organisation. In this case, both dendrimer generations G1 A5 and G2 A5 exhibit a hexagonal columnar mesophase.

The Syntheses and Structural Characterizations, Antimicrobial Activity and in Vitro Dna Binding of 4-Fluorobenzylspiro(n/O)cyclotriphosphazenes and Their Phosphazenium Salts

“…For instance, there are several studies in the literature on the reactions of cyclotriphosphazenes with NO donor type difunctional reagents [4][5][6]. Some of the cyclotriphosphazene derivatives are used as liquid crystals [7,8], rechargeable lithium-ion batteries [9,10], OLEDs [11,12], and lubricants [13,14]. It is found that aminocyclophosphazene derivatives have antimicrobial activity against bacteria and fungi [15][16][17].…”

Phosphorus–nitrogen compounds: part 30. Syntheses and structural investigations, antimicrobial and cytotoxic activities and DNA interactions of vanillinato-substituted NN or NO spirocyclic monoferrocenyl cyclotriphosphazenes

“…For example, it was found that spermine-bonded cyclotriphosphazenes disclosed cytotoxic activity against HT-29 (human colon adenocarcinoma), Hep2 (human epidermoid larynx carcinoma) and Vero (African green monkey kidney) cells and stimulated apoptosis [20]. Furthermore, some 1,4-dioxa-8-azaspiro [4,5] decane(DASD)-substituted ferrocenylphosphazenes were found to be effective against HeLa cancer cell lines [21]. In addition, aziridine-crown substituted cyclotriphosphazenes, known as the hazardous compounds, cleave the DNA and halt the growth of cancer cells [22].…”

“…Hexachloro cyclotriphosphazene (cyclic trimer, N 3 P 3 Cl 6 ) is a versatile starting compound for the syntheses of cyclotriphosphazene derivatives [1,2], polyorganophosphazenes [3,4] and dendrimers [5]. In the literature, a wide range of cyclotriphosphazene derivatives with different side groups and with diverse application potential were prepared using the replacement of highly reactive Cl-atoms in N 3 P 3 Cl 6 by a variety of -NH or -OH functionalized nucleophilic reagents, such as primary [6] and secondary amines [7], polyamines [8] and aryloxides [9].…”

Supermolecular Columnar Liquid‐Crystalline Phosphorus Dendrimers Decorated with Sulfonamide Derivatives

“…[11,12] Following a similar approach, a family of dendrimers up to the second generation was prepared, containing cyclotriphosphazene as a central rigid core and dendrons derived from 2,2-bis(hydroxymethyl)propionic acid, functionalized on their surface with mono-and polycatenar pro-mesogenic units. [10] Caminade and Majoral have described a well-known family of phosphorus dendrimers, poly-(phosphorhydrazone) dendrimers (PPH), based on this type of rigid core. [13] Although very interesting applications of these dendrimers have been proposed in the fields of catalysis, medicinal chemistry, and materials science, [14] to the best of our knowledge there has been no report concerning the preparation of liquid-crystalline macromolecules based on this system.…”

“…[8] Dendromesogens containing phosphorus atoms in their structures have been scarcely described in the literature. [9,10] Nevertheless, some of us have reported several series of unconventional mesogens derived from the cyclotriphosphazene ring, which can bear mesogenic units directly attached to the easily functionalized phosphorus atoms. [11,12] In those series, reaction of hydroquinone with hexachlorocyclotriphosphazene, followed by esterification of the peripheral hydroxyl groups with mono-or polycatenar benzoic acid derivatives, allowed the preparation of new liquid-crystalline compounds.…”