Francisco J. García Alonso

Soiling of building stones in urban environments

Abstract This paper studies the black soiling rate of building granite, marble and limestones in two urban environments with different climates. Specimens were placed horizontally, sheltered and unsheltered from rainfall. Colour changes were monitored. Changes in L ∗ were utilised to determine the total darkening of the stones and their soiling rate and were compared by statistical analysis. Black soiling depended on the type of stone and exposure. Limestones, mainly, showed a soiling proportional to the square root of the time of exposure. In this case, soiling coefficients could indicate frequency of necessary cleaning. The rest of the selected stones did not show such an evident relationship. The soiling tendency of all sheltered limestones was quite similar and more severe than in marble and granite. Soiling was related to the stone colour, type of voids and surface characteristics. Soiling of unsheltered specimens also seemed to depend on the rainfall conditions (rain periods, intensity, amount, temperature, etc.), which could influence both particle deposition and removal from stone surfaces.

Airborne particulate matter around the Cathedral of Burgos (Castilla y León, Spain)

A methodology to collect and analyse atmospheric particulate matter has been developed at the Cathedral of Burgos (Spain). Particles were collected in a portable particle sampler on carbon layers and stone surfaces. The analyses were undertaken under SEM-EDX by means X-ray mapping and Featurescan (a program for the automated characterisation of particles). To determine their possible sources, particles collected in the sampler and on carbon layers were classified according to their composition, mainly by cluster analysis. Then, they were compared with those deposited on stone surfaces. This classification is useful when a plan of preventive conservation for monuments is to be undertaken. In general, no important differences are observed between the chemical composition of particles directly collected from the atmosphere and those deposited on different substrates. Fine particles present the highest sulphur contents (almost 100%), while calcium is the major element in the medium and coarse particles. Other abundant elements are silicon, chlorine and phosphorus. The number of iron-rich particles is small. The study of the material deposited on carbon layers and stone substrates has confirmed the presence of gypsum in all cases.

On the synthesis of functionalized cyclic and polymeric aryloxyphosphazenes from phenols

A very convenient synthetic method is described for the known cyclic aryloxyphosphazenes [N3P3(OC6H4-R)6] (R = Br, CN, CHO, COCH3, COC6H5, and NO2). The method is based on the direct reaction of [N3P3Cl6] with six equivalents of the para-substituted phenols HOC6H4-R and K2CO3 in refluxing acetone and is characterized by very short reaction times and very simple workups, leading directly to the analytically and spectroscopically pure products in very high yields. In the cases where R = H, But, or OCH3, the reactions were much slower, but the time could be shortened by using [Bu4N]Br as the phase-transfer catalyst. Similarly, the polymers [NP(OC6H4-R)2]n can be conveniently obtained in ca. 70% and good analytical purity from polydichlorophosphazene [NPCl2]n and the para-substituted phenols HOC6H5-R (R = Br, CN, COCH3, and NO2) in the presence of K2CO3 using THF as the solvent.

INFRARED AND RAMAN SPECTRA OF THE PHOSPHAZENE HIGH POLYMER NP(O2C12H8)N

The vibrational spectra of a new type of phosphazene polymer, [NP(O2C12H8)]n (polyspirophosphazene), are discussed. The spectra were recorded for powders dispersed in KBr pellets and for films prepared from different solvents. The IR spectra are dominated by the vibrational modes of the main chain whereas the Raman spectra are dominated by the vibrations of the peripheral biphenyl groups. The full width at half maximum (FWHM) of the Raman band at 1609 cm-1, corresponding to one of the CC stretching modes of the biphenyl, decreases with increase in the degree of crystallinity of the polymer sample.

Synthesis, X-ray structure and coordination to Mn(CO)3(bipy)+ of the cyclotriphosphazenes N3P3(OC5H4N-2)6 and N3P3(OC5H4N-4)6

Abstract The hexachlorocyclotriphosphazene [N 3 P 3 Cl 6 ] reacts with 2-hydroxypyridine (HOC 5 H 4 N-2) and 4-hydroxypyridine (HOC 5 H 4 N-4) in acetone in the presence of K 2 CO 3 , to give the hexasubstituted products N 3 P 3 (OC 5 H 4 N-2) 6 ( 1 ) and N 3 P 3 (OC 5 H 4 N-4) 6 ( 2 ). The structure of both compounds has been determined by X-ray diffraction. The hexafunctionalized cyclotriphosphazene N 3 P 3 (OC 5 H 4 N-4) 6 ( 2 ) is a better ligand than 1 and reacts with fac -[Mn(OClO 3 )(CO) 3 (bipy)] in CH 2 Cl 2 to give the hexacationic complex [N 3 P 3 {(OC 5 H 4 N)Mn(CO) 3 (bipy)} 6 ](ClO 4 ) 6 ( 3 ).

Direct synthesis of cyclic and polymeric phosphazenes bearing diphenylphosphine groups and their complexes with [W(CO)5] fragments

Abstract The reactions of the cyclotriphosphazenes [N 3 P 3 Cl 6 ] or [N 3 P 3 (O 2 C 12 H 8 ) 2 Cl 2 ] with the phenolic phosphine PPh 2 (C 6 H 4 -OH) in the presence of Cs 2 CO 3 give, respectively, the cyclic phosphazene phosphines [N 3 P 3 (OC 6 H 4 PPh 2 ) 6 ] ( 1 ) and [N 3 P 3 (O 2 C 12 H 8 ) 2 (OC 6 H 4 PPh 2 ) 2 ] ( 2 ), very pure and in high yield. The similar reaction with the linear polyphosphazene {[NP(O 2 C 12 H 8 )] 0.65 [NPCl 2 ] 0.35 } n in THF gives the diphenylphosphine polymer {[NP(O 2 C 12 H 8 )] 0.65 [NP(OC 6 H 4 PPh 2 ) 2 ] 0.35 } n ( 3 ). The phenolic tungsten pentacarbonyl complex {W(CO) 5 [PPh 2 (C 6 H 4 -OH)]} reacts in the same way with those cyclic and polymeric phosphazenes to give the corresponding complexes {N 3 P 3 [OC 6 H 4 PPh 2 -W(CO) 5 ] 6 } ( 4 ), [N 3 P 3 (O 2 C 12 H 8 ) 2 (OC 6 H 4 PPh 2 -W(CO) 5 ) 2 ] ( 5 ), and {[NP(O 2 C 12 H 8 )] 0.65 [NP(OC 6 H 4 PPh 2 -W(CO) 5 ) 2 ] 0.35 } n ( 6 ).

Synthesis and spectroscopic properties of a new high molecular weight poly-spirophosphazene-oxypyridine copolymer and its complexes with W(CO)5 fragments

Abstract The polyspirophosphazene copolymer {[NP(O 2 C 12 H 8 )] 0.7 [NP(OC 5 H 4 N) 2 ] 0.3 } n ( 2 ); that carries pyridine side groups has been prepared from [NPCl 2 ] n , by reaction first with 2,2′-dihydroxybiphenyl and potassium carbonate in THF to give a solution of the partially substituted polymer {[NP(O 2 C 12 H 8 )] 0.7 [NPCl 2 ] 0.3 } n ( 1 ), followed by the reaction of the latter with 4-hydroxypyridine (HOC 5 H 4 N) also in the presence of potassium carbonate. The reaction of ( 2 ) with [W(HOMe)(CO) 5 ] in a CH 2 Cl 2 –MeOH mixture gave the polymeric complex {[NP(O 2 C 12 H 8 )] 0.7 [NP(OC 5 H 4 NW(CO) 5 ) 2 ] 0.3 } n ( 4 ), that, upon treatment with NCMe in THF produced derivatives with less metal carbonyl contents.

Surface changes on crystalline stones due to salt crystallisation

This study assesses the changes on the surface of crystalline stones due to salt crystallisation. Efflorescence was forced to grow on the surface of granite and marbles through 60 cycles of salt crystallisation with sodium sulphate. Changes on surface roughness, gloss and colour were measured every 15 cycles and the specimens were examined with naked eye and SEM. Sodium sulphate produces damage which depends on mineral composition. Results show that granites experience a mechanical decay with an increase in roughness. Peaks of mica can be observed on the surface and cracks widen and grow deeper. Colour and gloss do not show any significant change, although gloss decreases with an increase in surface roughness. In marbles, the decay is mainly chemical. Surface roughness increases due to dissolution of the calcite. White marbles exhibit yellowing. Gloss decreases during the first cycles—as grain boundaries become more visible—but tends to regain almost its initial value as the number of cycles increases. In this case, gloss does not show any relation with surface roughness.

Synthesis and spectroscopic characterization of cyclic and polymeric phosphazenes bearing phosphine complexes

Abstract The reactions of the cyclic phosphazenes [N 3 P 3 Cl 6 ] and [N 3 P 3 (O 2 C 12 H 8 ) 2 Cl 2 ] (O 2 C 12 H 8 =2,2′-dioxybiphenyl) with the diphenylphosphine phenol complex {Mn(CO) 2 (η 5 -C 5 H 4 Me)[PPh 2 (C 6 H 4 OH)]} ( 1 ) and Cs 2 CO 3 in refluxing acetone gave, respectively the phosphazene–phosphine complexes {N 3 P 3 [OC 6 H 4 PPh 2 Mn(CO) 2 (η 5 -C 5 H 4 Me)] 6 } ( 2 ) and {N 3 P 3 (O 2 C 12 H 8 ) 2 [OC 6 H 4 PPh 2 Mn(CO) 2 (η 5 -C 5 H 4 Me)] 2 } ( 3 ), in good yields. The analogous reaction of the partially substituted clorophosphazene polymer {[NP(O 2 C 12 H 8 )] 0.6 [NPCl 2 ] 0.4 } n in THF gave the polymeric complex [{NP(O 2 C 12 H 8 )} 0.6 {NP[OC 6 H 4 PPh 2 Mn(CO) 2 (η 5 -C 5 H 4 Me)] 2 } 0.4 ·0.5[OC 4 H 8 ] n ( 4 ). Different spectroscopic data are provided for the new compounds that may be useful for the characterization of other more complex polymeric materials.

Synthesis and 1H-, 15N-, 31P-, 183W-Multinuclear Magnetic Resonance Study of the Cyclotriphosphazenes [N3P3(dobp)2(OC5H4N-4)2] and [N3P3(dobp)(OC5H4N-4)4] and Their W(CO)5 Complexes (dobp = 2,2′-dioxybiphenyl)

The reactions of [N3P3(dobp)2Cl2] and [N3P3(dobp)Cl4] with a mixture of HOC5H4N-4 and K2CO3 in acetone give the cyclotriphosphazenes [N3P3(dobp)2(OC5H4N-4)2] and [N3P3(dobp)(OC5H4N-4)4], respectively. These compounds react with [W(MeOH)(CO)5] in methanol to give mixtures of the polymetallic complexes [N3P3(dobp)2(OC5H4N-4)2{W(CO)5}x] (x = 1, 2) and [N3P3(dobp)(OC5H4N-4)4{W(CO)5}x] (x = 1–4), which are unstable in solution, slowly undergoing loss of the pentacarbonyl moiety. A complete characterization by multinuclear 1H, 15N, 31P, 183W magnetic resonance has revealed that the complexation of the N atom of one 4-oxypyridine ligand by the W(CO)5 fragment has a measurable effect on other parts of the phosphazene molecule very far away from the coordination site. The changes observed in δ183W have been used to identify the components in mixtures of compounds incorporating different numbers of tungsten atoms in the molecule. The characterization of less sensitive nuclei has been accomplished by means of indirect detection methods.