Order−Disorder Phase Transition in Poly(di-n-butylstannane) Observed by UV−Vis and Raman Spectroscopy

Abstract

Variable-temperature UV-vis and Raman spectra have enabled detection of a thermochromic phase transition for [ n Bu2Sn]n with an onset temperature Tc at ca. 260 K. The exact Tc value depends on the sample prehistory and the rate of cooling. This transition proceeds over a temperature interval from ca. 260 to ca. 200 K, when it reaches completion, and it involves two modifications: one with a disordered polymer backbone, which corresponds to a UV band at ca. 390 nm and a broad Raman feature for the ν(Sn-Sn) mode at ca. 120 cm -1 , and a more ordered one (apparently, all-anti or transoid), to which a red-shifted UV band at ca. 420 nm and a very intense narrow Raman line for the ν(Sn-Sn) mode at ca. 145 cm -1 are assigned. No abrupt side chain ordering was observed at Tc, but a gradual ordering, involving rotational isomerism about the C-C bonds, occurs on further lowering of the temperature. Comparison is made with data obtained for other polystannanes [ n R2Sn]n (R ) n-hexyl, n-octyl).

Organotin compounds bearing mesogenic sidechains: synthesis, X-ray structures and polymerisation chemistry

“…This conformational ordering can be induced by appropriate alignment of the sidechain substituents, and was first noticed in the case of [( n Hex) 2 Si] n [15] which shows a thermochromic shift in the sÁ/s* transition from 374 nm in an ordered film to 317 nm when the same film is heated to 100 8C [15]. Similar effects have been noted in the case of polystannanes [1,2,16].…”

From poly(dialkylstannane)s to poly(diarylstannane)s: comparison of synthesis methods and resulting polymers

“…However, besides the nature of the side chains, the conformation of the polystannane main chain may also influence λ max . This phenomenon is well known for polysilanes [35] and was also described for polystannanes, where delocalization was found to be maximal for planar zigzag structures [5,36] . Thus, part of the poly(diphenylstannane) 1 might be present in the planar zigzag conformation, leading to a low band gap polymer with a pronounced bathochromic shift of the absorption maximum.…”

Stabilizing, non-covalent interactions in the solid state structure of novel aryltin hydrides and halogenides

“…47 Furthermore in the last decade, organotin dihydrides (R 2 SnH 2 ) have been explored as precursors in the formation of polymeric materials exhibiting a linear backbone of covalently bonded tin atoms. 28,[48][49] However, the solid state structures of organotin hydrides have not been well studied. While alkyl tin hydrides are liquid, the only solid state examples of aryltin hydrides known to date have been isolated by our working group and include mesityl 2 SnH 2 , 28 phenyl 3 SnH, 44 and 2,6-xylyl 3 SnH (8) ( Table 3).…”