Combined LCA and Green Metrics Approach for the Sustainability Assessment of an Organic Dye Synthesis on Lab Scale

Abstract

New generation photovoltaic devices have attracted much attention in the last decades since they can be efficiently manufactured employing abundant raw materials and with less-energy intensive processes. In this context, the use of powerful environmental assessment is pivotal to support the fine-tuning of solar cells fabrication and hit the target of manufacturing effective sustainable technological devices. In this work, a mass-based green metrics and life cycle assessment combined approach is applied to analyze the environmental performances of an innovative synthetic protocol for the preparation of organic dye TTZ5, which has been successfully proposed as sensitizer for manufacturing dye sensitized solar cells. The new synthetic strategy, which is based on the C-H activation process, has been compared with the previously reported synthesis employing classic Suzuki-Miyaura cross-coupling chemistry. Results highlight the contribution of direct energy consumption and purification operations in organic syntheses at lab scale. Furthermore, they demonstrate the usefulness of the environmental multifaceted analytic tool and the power of life cycle assessment to overcome the intrinsic less comprehensive nature of green metrics for the evaluation of organic synthetic protocols.

Thiazolo[5,4-d]thiazole-based organic sensitizers with improved spectral properties for application in greenhouse-integrated dye-sensitized solar cells

“…Our aim was to accomplish the synthesis of dyes TTZ8-12 extending the scope of our new one-pot direct arylation protocol, previously designed for the gram-scale synthesis of the parent compound TTZ5. 56 Such a procedure allows the introduction of both donor and acceptor moieties onto the thiazolothiazole-based skeleton 1 in just one step through two consecutive Pd-catalyzed C-H activation reactions (Scheme 1). While the proper donor fragment 2 was prepared according to a previously reported procedure, 36 appropriate synthetic procedures had to be devised for each of the ve necessary bromine-containing (hetero)aryl aldehydes 3-7.…”

Route efficiency assessment and review of the synthesis of β-nucleosides via N-glycosylation of nucleobases

“…This observation is somewhat intuitive as nucleobases and many nucleosides are generally poorly soluble in all solvents and solvents are known to be the main determiner for E-factors, if they are included in the calculation. 11,36,44,45 Nonetheless, we were surprised to find that even routes which employed heterogenous steps were characterized by overshadowing solvent contributions. Biocatalytic routes were particularly plagued by the low water solubility of many nucleobases, which has so far largely restricted these syntheses to working concentrations in the low millimolar range.…”

“…To still permit a calculation of cEF (which includes, for example, reaction solvents and solutions for quenching and extractions), several quantities had to be estimated. We based these estimates on previous reports of this kind, 45 original papers on the matter 44,103 as well as our own experience with typical laboratory procedures. A complete and transparent description of all calculations and estimates is given in the ESI.…”

“…Depending on the solvent used and the crude product, this equaled a cEF contribution of around 500-1500 per chromatography step in most cases. Considering published experimental data on this issue, 44,103 and the fact that most chromatography steps in our dataset were done to isolate material from complex mixtures, this is a very conservative estimate for most syntheses analyzed here. Still, chromatography solvents dominated the cEFs of all routes that employed chromatographic purifications.…”

“…[20][21][22][23][24][25] Beyond that, assessments of individual newly published reactions or approaches versus established methods have become a common sight in the literature and continue to provide a valuable and critical evaluation of the state of the art. [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45] However, most of the above approaches focus either on (i) drug-like molecules and, consequently, the heterocycle chemistry commonly involved or (ii) single transformations. To the best of our knowledge, a comprehensive assessment of sustainability or efficiency for glycosylation-type chemistry is missing from the literature.…”